Easy: Add build date and commit revision to log
Easy: Add build date and commit revision to log

Summary:
We're getting bug reports from users where it's not clear
exactly what revision of Buck they're running.

This adds the build date and commit revision to the log.

It looks like this:

  [com.facebook.buck.cli.Main] Starting up (build date 2014-10-16
  13:55:56 -0700, rev 6476c6a9564c0fef7f30b96ef5278e8426298b32), args:
  [build, buck]

Test Plan: buck build buck, saw above message in logs

hgl888/buck,Heart2009/buck,vschs007/buck,rmaz/buck,raviagarwal7/buck,clonetwin26/buck,Addepar/buck,LegNeato/buck,mnuessler/buck,pwz3n0/buck,janicduplessis/buck,pwz3n0/buck,shybovycha/buck,nguyentruongtho/buck,janicduplessis/buck,Dominator008/buck,darkforestzero/buck,mikekap/buck,tgummerer/buck,brettwooldridge/buck,Learn-Android-app/buck,JoelMarcey/buck,mogers/buck,stuhood/buck,luiseduardohdbackup/buck,JoelMarcey/buck,janicduplessis/buck,sdwilsh/buck,mogers/buck,tgummerer/buck,artiya4u/buck,vschs007/buck,darkforestzero/buck,SeleniumHQ/buck,Learn-Android-app/buck,OkBuilds/buck,zpao/buck,zhuxiaohao/buck,JoelMarcey/buck,k21/buck,SeleniumHQ/buck,luiseduardohdbackup/buck,daedric/buck,hgl888/buck,MarkRunWu/buck,mogers/buck,dsyang/buck,mikekap/buck,robbertvanginkel/buck,shybovycha/buck,JoelMarcey/buck,bocon13/buck,dpursehouse/buck,mnuessler/buck,luiseduardohdbackup/buck,dushmis/buck,dsyang/buck,robbertvanginkel/buck,facebook/buck,ilya-klyuchnikov/buck,janicduplessis/buck,daedric/buck,sdwilsh/buck,rmaz/buck,Distrotech/buck,JoelMarcey/buck,lukw00/buck,Learn-Android-app/buck,dushmis/buck,mikekap/buck,robbertvanginkel/buck,romanoid/buck,sdwilsh/buck,rhencke/buck,ilya-klyuchnikov/buck,nguyentruongtho/buck,tgummerer/buck,tgummerer/buck,nguyentruongtho/buck,dpursehouse/buck,stuhood/buck,JoelMarcey/buck,SeleniumHQ/buck,dsyang/buck,Distrotech/buck,rmaz/buck,pwz3n0/buck,dsyang/buck,neonichu/buck,romanoid/buck,shs96c/buck,robbertvanginkel/buck,artiya4u/buck,bocon13/buck,MarkRunWu/buck,liuyang-li/buck,tgummerer/buck,1yvT0s/buck,ilya-klyuchnikov/buck,LegNeato/buck,Distrotech/buck,shybovycha/buck,OkBuilds/buck,dushmis/buck,romanoid/buck,Learn-Android-app/buck,darkforestzero/buck,Addepar/buck,hgl888/buck,sdwilsh/buck,mikekap/buck,facebook/buck,JoelMarcey/buck,dpursehouse/buck,lukw00/buck,Learn-Android-app/buck,marcinkwiatkowski/buck,zpao/buck,brettwooldridge/buck,lukw00/buck,OkBuilds/buck,mikekap/buck,clonetwin26/buck,shs96c/buck,luiseduardohdbackup/buck,neonichu/buck,lukw00/buck,vschs007/buck,rhencke/buck,grumpyjames/buck,hgl888/buck,mogers/buck,siddhartharay007/buck,1yvT0s/buck,rowillia/buck,Dominator008/buck,hgl888/buck,vschs007/buck,siddhartharay007/buck,shs96c/buck,LegNeato/buck,siddhartharay007/buck,davido/buck,illicitonion/buck,clonetwin26/buck,kageiit/buck,luiseduardohdbackup/buck,justinmuller/buck,bocon13/buck,sdwilsh/buck,k21/buck,raviagarwal7/buck,darkforestzero/buck,k21/buck,rhencke/buck,neonichu/buck,brettwooldridge/buck,raviagarwal7/buck,LegNeato/buck,1yvT0s/buck,Heart2009/buck,luiseduardohdbackup/buck,liuyang-li/buck,vine/buck,lukw00/buck,vschs007/buck,zhan-xiong/buck,stuhood/buck,shs96c/buck,lukw00/buck,janicduplessis/buck,darkforestzero/buck,raviagarwal7/buck,darkforestzero/buck,SeleniumHQ/buck,facebook/buck,robbertvanginkel/buck,robbertvanginkel/buck,clonetwin26/buck,grumpyjames/buck,janicduplessis/buck,1yvT0s/buck,brettwooldridge/buck,rowillia/buck,MarkRunWu/buck,vine/buck,neonichu/buck,daedric/buck,shs96c/buck,rowillia/buck,zpao/buck,shybovycha/buck,daedric/buck,LegNeato/buck,mnuessler/buck,neonichu/buck,daedric/buck,mnuessler/buck,ilya-klyuchnikov/buck,raviagarwal7/buck,hgl888/buck,clonetwin26/buck,shs96c/buck,SeleniumHQ/buck,raviagarwal7/buck,shs96c/buck,liuyang-li/buck,grumpyjames/buck,robbertvanginkel/buck,rowillia/buck,rowillia/buck,vine/buck,romanoid/buck,brettwooldridge/buck,brettwooldridge/buck,Addepar/buck,MarkRunWu/buck,Dominator008/buck,tgummerer/buck,ilya-klyuchnikov/buck,rmaz/buck,Addepar/buck,tgummerer/buck,luiseduardohdbackup/buck,marcinkwiatkowski/buck,romanoid/buck,rmaz/buck,zhan-xiong/buck,facebook/buck,SeleniumHQ/buck,OkBuilds/buck,ilya-klyuchnikov/buck,Addepar/buck,grumpyjames/buck,justinmuller/buck,mnuessler/buck,brettwooldridge/buck,OkBuilds/buck,rmaz/buck,raviagarwal7/buck,romanoid/buck,janicduplessis/buck,grumpyjames/buck,rhencke/buck,vschs007/buck,shybovycha/buck,ilya-klyuchnikov/buck,vschs007/buck,neonichu/buck,nguyentruongtho/buck,liuyang-li/buck,romanoid/buck,rmaz/buck,vschs007/buck,raviagarwal7/buck,darkforestzero/buck,k21/buck,artiya4u/buck,Learn-Android-app/buck,mikekap/buck,sdwilsh/buck,pwz3n0/buck,bocon13/buck,grumpyjames/buck,tgummerer/buck,kageiit/buck,romanoid/buck,marcinkwiatkowski/buck,1yvT0s/buck,vschs007/buck,liuyang-li/buck,sdwilsh/buck,Heart2009/buck,janicduplessis/buck,artiya4u/buck,dsyang/buck,liuyang-li/buck,zpao/buck,illicitonion/buck,mogers/buck,robbertvanginkel/buck,OkBuilds/buck,raviagarwal7/buck,LegNeato/buck,rmaz/buck,LegNeato/buck,Learn-Android-app/buck,k21/buck,justinmuller/buck,clonetwin26/buck,vschs007/buck,lukw00/buck,dsyang/buck,raviagarwal7/buck,SeleniumHQ/buck,mogers/buck,darkforestzero/buck,bocon13/buck,clonetwin26/buck,tgummerer/buck,romanoid/buck,OkBuilds/buck,rhencke/buck,zhan-xiong/buck,bocon13/buck,rowillia/buck,Dominator008/buck,shybovycha/buck,marcinkwiatkowski/buck,siddhartharay007/buck,marcinkwiatkowski/buck,robbertvanginkel/buck,kageiit/buck,dushmis/buck,marcinkwiatkowski/buck,rmaz/buck,mogers/buck,marcinkwiatkowski/buck,marcinkwiatkowski/buck,JoelMarcey/buck,janicduplessis/buck,justinmuller/buck,Dominator008/buck,brettwooldridge/buck,brettwooldridge/buck,artiya4u/buck,zhuxiaohao/buck,zhan-xiong/buck,davido/buck,SeleniumHQ/buck,rhencke/buck,LegNeato/buck,bocon13/buck,illicitonion/buck,zhuxiaohao/buck,darkforestzero/buck,zhan-xiong/buck,zhan-xiong/buck,raviagarwal7/buck,rhencke/buck,Heart2009/buck,darkforestzero/buck,robbertvanginkel/buck,vine/buck,kageiit/buck,Heart2009/buck,robbertvanginkel/buck,davido/buck,zhuxiaohao/buck,rhencke/buck,mogers/buck,liuyang-li/buck,ilya-klyuchnikov/buck,siddhartharay007/buck,k21/buck,shybovycha/buck,SeleniumHQ/buck,Heart2009/buck,dsyang/buck,Addepar/buck,JoelMarcey/buck,luiseduardohdbackup/buck,pwz3n0/buck,hgl888/buck,zhan-xiong/buck,liuyang-li/buck,justinmuller/buck,Dominator008/buck,bocon13/buck,neonichu/buck,pwz3n0/buck,justinmuller/buck,shybovycha/buck,romanoid/buck,SeleniumHQ/buck,pwz3n0/buck,Learn-Android-app/buck,Dominator008/buck,LegNeato/buck,vine/buck,justinmuller/buck,stuhood/buck,Distrotech/buck,lukw00/buck,grumpyjames/buck,artiya4u/buck,OkBuilds/buck,liuyang-li/buck,k21/buck,davido/buck,dushmis/buck,mikekap/buck,Learn-Android-app/buck,marcinkwiatkowski/buck,mikekap/buck,zhan-xiong/buck,brettwooldridge/buck,shs96c/buck,SeleniumHQ/buck,rowillia/buck,zhan-xiong/buck,marcinkwiatkowski/buck,davido/buck,brettwooldridge/buck,rhencke/buck,ilya-klyuchnikov/buck,clonetwin26/buck,mikekap/buck,artiya4u/buck,Learn-Android-app/buck,bocon13/buck,raviagarwal7/buck,vine/buck,rmaz/buck,tgummerer/buck,brettwooldridge/buck,tgummerer/buck,clonetwin26/buck,vschs007/buck,marcinkwiatkowski/buck,zhan-xiong/buck,luiseduardohdbackup/buck,zhuxiaohao/buck,grumpyjames/buck,siddhartharay007/buck,janicduplessis/buck,shybovycha/buck,Learn-Android-app/buck,janicduplessis/buck,Distrotech/buck,facebook/buck,sdwilsh/buck,OkBuilds/buck,justinmuller/buck,LegNeato/buck,neonichu/buck,kageiit/buck,shs96c/buck,kageiit/buck,ilya-klyuchnikov/buck,k21/buck,zhuxiaohao/buck,artiya4u/buck,hgl888/buck,rowillia/buck,zpao/buck,dsyang/buck,mikekap/buck,MarkRunWu/buck,mikekap/buck,illicitonion/buck,LegNeato/buck,Distrotech/buck,Addepar/buck,clonetwin26/buck,dushmis/buck,dsyang/buck,Distrotech/buck,dsyang/buck,1yvT0s/buck,rmaz/buck,Dominator008/buck,dpursehouse/buck,Addepar/buck,lukw00/buck,mogers/buck,daedric/buck,grumpyjames/buck,dpursehouse/buck,davido/buck,pwz3n0/buck,sdwilsh/buck,raviagarwal7/buck,davido/buck,davido/buck,daedric/buck,grumpyjames/buck,dushmis/buck,Distrotech/buck,JoelMarcey/buck,vine/buck,MarkRunWu/buck,mikekap/buck,davido/buck,sdwilsh/buck,lukw00/buck,zhan-xiong/buck,MarkRunWu/buck,justinmuller/buck,marcinkwiatkowski/buck,vschs007/buck,Distrotech/buck,marcinkwiatkowski/buck,illicitonion/buck,Addepar/buck,JoelMarcey/buck,sdwilsh/buck,shs96c/buck,nguyentruongtho/buck,zpao/buck,robbertvanginkel/buck,ilya-klyuchnikov/buck,shybovycha/buck,Heart2009/buck,brettwooldridge/buck,romanoid/buck,bocon13/buck,k21/buck,ilya-klyuchnikov/buck,rmaz/buck,mnuessler/buck,facebook/buck,OkBuilds/buck,mnuessler/buck,rmaz/buck,Addepar/buck,daedric/buck,stuhood/buck,daedric/buck,artiya4u/buck,davido/buck,hgl888/buck,vine/buck,ilya-klyuchnikov/buck,siddhartharay007/buck,nguyentruongtho/buck,illicitonion/buck,OkBuilds/buck,illicitonion/buck,pwz3n0/buck,1yvT0s/buck,k21/buck,darkforestzero/buck,illicitonion/buck,dpursehouse/buck,stuhood/buck,rowillia/buck,vine/buck,sdwilsh/buck,JoelMarcey/buck,davido/buck,robbertvanginkel/buck,shs96c/buck,illicitonion/buck,vine/buck,dushmis/buck,darkforestzero/buck,dpursehouse/buck,illicitonion/buck,darkforestzero/buck,grumpyjames/buck,rhencke/buck,Heart2009/buck,Dominator008/buck,rhencke/buck,artiya4u/buck,Dominator008/buck,clonetwin26/buck,dsyang/buck,rowillia/buck,LegNeato/buck,siddhartharay007/buck,mogers/buck,justinmuller/buck,Addepar/buck,grumpyjames/buck,Distrotech/buck,pwz3n0/buck,davido/buck,OkBuilds/buck,zhuxiaohao/buck,rowillia/buck,stuhood/buck,lukw00/buck,SeleniumHQ/buck,janicduplessis/buck,daedric/buck,pwz3n0/buck,mnuessler/buck,davido/buck,dpursehouse/buck,dushmis/buck,stuhood/buck,Distrotech/buck,Heart2009/buck,justinmuller/buck,OkBuilds/buck,artiya4u/buck,k21/buck,1yvT0s/buck,Addepar/buck,1yvT0s/buck,dsyang/buck,mogers/buck,illicitonion/buck,zhuxiaohao/buck,romanoid/buck,stuhood/buck,Addepar/buck,zpao/buck,stuhood/buck,vschs007/buck,illicitonion/buck,vine/buck,sdwilsh/buck,stuhood/buck,justinmuller/buck,daedric/buck,romanoid/buck,shs96c/buck,bocon13/buck,neonichu/buck,nguyentruongtho/buck,dsyang/buck,illicitonion/buck,dushmis/buck,liuyang-li/buck,k21/buck,zhan-xiong/buck,zhuxiaohao/buck,zhan-xiong/buck,kageiit/buck,JoelMarcey/buck,shybovycha/buck,shybovycha/buck,justinmuller/buck,LegNeato/buck,MarkRunWu/buck,Dominator008/buck,shs96c/buck,siddhartharay007/buck,shybovycha/buck,Dominator008/buck,daedric/buck,bocon13/buck,clonetwin26/buck,mnuessler/buck,facebook/buck,liuyang-li/buck,daedric/buck,rowillia/buck,SeleniumHQ/buck,k21/buck,clonetwin26/buck