Add mercurial to dependencies in readme
Add mercurial to dependencies in readme

Using `go get` runs `hg` which is not installed by default, update README
to suggest getting it as well as bzr and git.

alesstimec/juju,ericsnowcurrently/juju,bac/juju,alesstimec/juju,dooferlad/juju,cherylj/juju,davecheney/juju,thomnico/juju,kat-co/juju,kat-co/juju,kat-co/juju,davecheney/juju,cloud-green/juju,rogpeppe/juju,mjs/juju,cmars/juju,marcmolla/juju,frobware/juju,frobware/juju,gabriel-samfira/juju,mikemccracken/juju,tasdomas/juju,sinzui/juju,cloud-green/juju,mattyw/juju,waigani/juju,frankban/juju,makyo/juju,mjs/juju,anastasiamac/juju,bogdanteleaga/juju,macgreagoir/juju,wwitzel3/juju,voidspace/juju,mjs/juju,bogdanteleaga/juju,reedobrien/store,mattyw/juju,anastasiamac/juju,thomnico/juju,gabriel-samfira/juju,frobware/juju,wwitzel3/juju,mikemccracken/juju,howbazaar/juju,tasdomas/juju,ericsnowcurrently/juju,kat-co/juju,axw/juju,cherylj/juju,ericsnowcurrently/juju,tasdomas/juju,sinzui/juju,marcmolla/juju,mjs/juju,cherylj/juju,gabriel-samfira/juju,AdamIsrael/juju,thomnico/juju,howbazaar/juju,cmars/juju,bac/juju,AdamIsrael/juju,jrwren/juju,Altoros/juju-vmware,mikemccracken/juju,alesstimec/juju,AdamIsrael/juju,frankban/juju,bac/juju,bac/juju,alesstimec/juju,mikemccracken/juju,fwereade/juju,waigani/juju,AdamIsrael/juju,anastasiamac/juju,sinzui/juju,gabriel-samfira/juju,axw/juju,axw/juju,dimitern/juju,voidspace/juju,frankban/juju,frankban/juju-tmp,mhilton/juju-juju,waigani/juju,frankban/juju,dooferlad/juju,mjs/juju,perrito666/juju,macgreagoir/juju,fwereade/juju,cmars/juju,dimitern/juju,Altoros/juju-vmware,macgreagoir/juju,makyo/juju,bac/juju,tsakas/juju,perrito666/juju,voidspace/juju,perrito666/juju,marcoceppi/juju,wwitzel3/juju,mhilton/juju,makyo/juju,tsakas/juju,reedobrien/juju,marcmolla/juju,dimitern/juju,Altoros/juju-vmware,Altoros/juju-cloudsigma,anastasiamac/juju,mhilton/juju-juju,makyo/juju,cloud-green/juju,dooferlad/juju,perrito666/juju,cherylj/juju,bogdanteleaga/juju,frankban/juju-tmp,howbazaar/juju,rogpeppe/juju,davecheney/juju,kat-co/juju,mjs/juju,tych0/juju,dooferlad/juju,marcmolla/juju,fwereade/juju,Altoros/juju-cloudsigma,dooferlad/juju,axw/juju,reedobrien/juju,bz2/juju,macgreagoir/juju,tych0/juju,howbazaar/juju,mhilton/juju-juju,macgreagoir/juju,sinzui/juju,reedobrien/juju,tasdomas/juju,mhilton/juju-juju,mhilton/juju,tsakas/juju,fwereade/juju,waigani/juju,axw/juju,mhilton/juju,reedobrien/juju,thomnico/juju,jrwren/juju,mhilton/juju,marcmolla/juju,voidspace/juju,bz2/juju,frankban/juju-tmp,dimitern/juju,frankban/juju,howbazaar/juju,frankban/juju-tmp,anastasiamac/juju,tych0/juju,marcoceppi/juju,Altoros/juju-vmware,mikemccracken/juju,tsakas/juju,ericsnowcurrently/juju,wwitzel3/juju,cloud-green/juju,mjs/juju,bz2/juju,bz2/juju,gabriel-samfira/juju,reedobrien/juju,tych0/juju,marcoceppi/juju,marcoceppi/juju,perrito666/juju,alesstimec/juju,ericsnowcurrently/juju,rogpeppe/juju,bz2/juju,dimitern/juju,Altoros/juju-cloudsigma,bogdanteleaga/juju,Altoros/juju-cloudsigma,mattyw/juju,jrwren/juju,davecheney/juju,mattyw/juju,cmars/juju