fix chef version checking
fix chef version checking

the version checking here uses a function which is intended only
for chef cookbook versions, which must be x.y or x.y.z.  when fed
a legal chef prerelease version the prior code throws an exception:

[2014-05-01T22:08:01+00:00] FATAL: Configuration error Chef::Exceptions::InvalidCookbookVersion: '11.14.0.alpha.1' does not match 'x.y.z' or 'x.y'
[2014-05-01T22:08:01+00:00] FATAL:   /tmp/vagrant-chef-2/solo.rb:6:in `from_string'
[2014-05-01T22:08:01+00:00] FATAL: Aborting due to error in '/tmp/vagrant-chef-2/solo.rb'

since we only need to compare the major and minor version numbers a
simple #to_f sufficies for this test.

alternative, we could use Gem::Version here, but i didn't really see
the need to...

tbarrongh/vagrant,vamegh/vagrant,bdwyertech/vagrant,blueyed/vagrant,Chhunlong/vagrant,bdwyertech/vagrant,dustymabe/vagrant,vamegh/vagrant,lonniev/vagrant,BlakeMesdag/vagrant,marxarelli/vagrant,kamigerami/vagrant,dhoer/vagrant,PatrickLang/vagrant,teotihuacanada/vagrant,tomfanning/vagrant,sax/vagrant,bdwyertech/vagrant,mkuzmin/vagrant,mwarren/vagrant,jmanero/vagrant,invernizzi-at-google/vagrant,bshurts/vagrant,benh57/vagrant,philoserf/vagrant,bshurts/vagrant,channui/vagrant,nickryand/vagrant,PatrickLang/vagrant,doy/vagrant,chrisroberts/vagrant,jberends/vagrant,krig/vagrant,Sgoettschkes/vagrant,mwrock/vagrant,rivy/vagrant,sni/vagrant,chrisroberts/vagrant,wangfakang/vagrant,signed8bit/vagrant,ferventcoder/vagrant,justincampbell/vagrant,ianmiell/vagrant,channui/vagrant,gbarberi/vagrant,sideci-sample/sideci-sample-vagrant,lonniev/vagrant,dhoer/vagrant,apertoso/vagrant,ArloL/vagrant,TheBigBear/vagrant,tbriggs-curse/vagrant,jean/vagrant,tschortsch/vagrant,Sgoettschkes/vagrant,denisbr/vagrant,jkburges/vagrant,jtopper/vagrant,taliesins/vagrant,denisbr/vagrant,aneeshusa/vagrant,Avira/vagrant,aneeshusa/vagrant,dustymabe/vagrant,benh57/vagrant,philoserf/vagrant,modulexcite/vagrant,justincampbell/vagrant,bheuvel/vagrant,chrisvire/vagrant,miguel250/vagrant,johntron/vagrant,mwrock/vagrant,darkn3rd/vagrant,benizi/vagrant,tomfanning/vagrant,jean/vagrant,gitebra/vagrant,iNecas/vagrant,PatOShea/vagrant,bryson/vagrant,tbriggs-curse/vagrant,bryson/vagrant,dustymabe/vagrant,mwarren/vagrant,petems/vagrant,philwrenn/vagrant,chrisvire/vagrant,jtopper/vagrant,BlakeMesdag/vagrant,otagi/vagrant,sni/vagrant,benh57/vagrant,lonniev/vagrant,muhanadra/vagrant,justincampbell/vagrant,johntron/vagrant,lukebakken/vagrant,pwnall/vagrant,ArloL/vagrant,aaam/vagrant,mpoeter/vagrant,PatOShea/vagrant,jmanero/vagrant,jkburges/vagrant,apertoso/vagrant,fnewberg/vagrant,senglin/vagrant,jtopper/vagrant,tknerr/vagrant,marxarelli/vagrant,tjanez/vagrant,genome21/vagrant,h4ck3rm1k3/vagrant,philwrenn/vagrant,lonniev/vagrant,gbarberi/vagrant,teotihuacanada/vagrant,Chhunlong/vagrant,loren-osborn/vagrant,juiceinc/vagrant,myrjola/vagrant,jkburges/vagrant,TheBigBear/vagrant,tjanez/vagrant,signed8bit/vagrant,muhanadra/vagrant,wkolean/vagrant,senglin/vagrant,modulexcite/vagrant,theist/vagrant,lukebakken/vagrant,crashlytics/vagrant,patrys/vagrant,sax/vagrant,iNecas/vagrant,jean/vagrant,jkburges/vagrant,Sgoettschkes/vagrant,mitchellh/vagrant,tbarrongh/vagrant,jfchevrette/vagrant,jhoblitt/vagrant,bheuvel/vagrant,modulexcite/vagrant,Chhunlong/vagrant,vamegh/vagrant,gpkfr/vagrant,kalabiyau/vagrant,Endika/vagrant,kamigerami/vagrant,shtouff/vagrant,tomfanning/vagrant,iNecas/vagrant,mitchellh/vagrant,rivy/vagrant,genome21/vagrant,shtouff/vagrant,gpkfr/vagrant,senglin/vagrant,tschortsch/vagrant,mwarren/vagrant,sax/vagrant,Sgoettschkes/vagrant,blueyed/vagrant,gbarberi/vagrant,aaam/vagrant,kamazee/vagrant,marxarelli/vagrant,jtopper/vagrant,mpoeter/vagrant,sideci-sample/sideci-sample-vagrant,jmanero/vagrant,tomfanning/vagrant,aaam/vagrant,miguel250/vagrant,evverx/vagrant,chrisroberts/vagrant,tbarrongh/vagrant,mpoeter/vagrant,dharmab/vagrant,dustymabe/vagrant,teotihuacanada/vagrant,petems/vagrant,invernizzi-at-google/vagrant,evverx/vagrant,philwrenn/vagrant,PatrickLang/vagrant,invernizzi-at-google/vagrant,mkuzmin/vagrant,dhoer/vagrant,tknerr/vagrant,chrisroberts/vagrant,bshurts/vagrant,janek-warchol/vagrant,h4ck3rm1k3/vagrant,benh57/vagrant,nickryand/vagrant,ArloL/vagrant,zsjohny/vagrant,jberends/vagrant,aneeshusa/vagrant,taliesins/vagrant,loren-osborn/vagrant,clinstid/vagrant,Chhed13/vagrant,jhoblitt/vagrant,tknerr/vagrant,h4ck3rm1k3/vagrant,jmanero/vagrant,ArloL/vagrant,ferventcoder/vagrant,dharmab/vagrant,Avira/vagrant,rivy/vagrant,nickryand/vagrant,theist/vagrant,zsjohny/vagrant,stephancom/vagrant,wangfakang/vagrant,patrys/vagrant,sideci-sample/sideci-sample-vagrant,aneeshusa/vagrant,pwnall/vagrant,kamigerami/vagrant,Endika/vagrant,krig/vagrant,zsjohny/vagrant,justincampbell/vagrant,mwarren/vagrant,clinstid/vagrant,denisbr/vagrant,juiceinc/vagrant,gajdaw/vagrant,denisbr/vagrant,myrjola/vagrant,ferventcoder/vagrant,Avira/vagrant,taliesins/vagrant,obnoxxx/vagrant,Endika/vagrant,myrjola/vagrant,otagi/vagrant,jfchevrette/vagrant,marxarelli/vagrant,mwrock/vagrant,jfchevrette/vagrant,dharmab/vagrant,doy/vagrant,obnoxxx/vagrant,gitebra/vagrant,dhoer/vagrant,pwnall/vagrant,PatOShea/vagrant,blueyed/vagrant,jhoblitt/vagrant,kalabiyau/vagrant,loren-osborn/vagrant,sax/vagrant,janek-warchol/vagrant,modulexcite/vagrant,janek-warchol/vagrant,wkolean/vagrant,legal90/vagrant,mpoeter/vagrant,chrisvire/vagrant,philwrenn/vagrant,channui/vagrant,patrys/vagrant,sni/vagrant,sni/vagrant,mkuzmin/vagrant,stephancom/vagrant,jberends/vagrant,johntron/vagrant,cgvarela/vagrant,darkn3rd/vagrant,kamigerami/vagrant,cgvarela/vagrant,lukebakken/vagrant,krig/vagrant,aaam/vagrant,gitebra/vagrant,mkuzmin/vagrant,theist/vagrant,kalabiyau/vagrant,jean/vagrant,darkn3rd/vagrant,teotihuacanada/vagrant,lukebakken/vagrant,obnoxxx/vagrant,BlakeMesdag/vagrant,muhanadra/vagrant,petems/vagrant,darkn3rd/vagrant,dharmab/vagrant,tbriggs-curse/vagrant,gitebra/vagrant,kalabiyau/vagrant,Chhed13/vagrant,stephancom/vagrant,legal90/vagrant,carlosefr/vagrant,doy/vagrant,petems/vagrant,wkolean/vagrant,otagi/vagrant,stephancom/vagrant,mitchellh/vagrant,tschortsch/vagrant,wkolean/vagrant,patrys/vagrant,Endika/vagrant,gbarberi/vagrant,signed8bit/vagrant,tschortsch/vagrant,legal90/vagrant,clinstid/vagrant,miguel250/vagrant,MiLk/vagrant,bheuvel/vagrant,tjanez/vagrant,h4ck3rm1k3/vagrant,Avira/vagrant,tbriggs-curse/vagrant,rivy/vagrant,ianmiell/vagrant,ianmiell/vagrant,taliesins/vagrant,Chhunlong/vagrant,vamegh/vagrant,MiLk/vagrant,Chhed13/vagrant,senglin/vagrant,TheBigBear/vagrant,philoserf/vagrant,gpkfr/vagrant,shtouff/vagrant,shtouff/vagrant,chrisvire/vagrant,philoserf/vagrant,jhoblitt/vagrant,fnewberg/vagrant,ianmiell/vagrant,signed8bit/vagrant,bryson/vagrant,crashlytics/vagrant,muhanadra/vagrant,nickryand/vagrant,mwrock/vagrant,bryson/vagrant,otagi/vagrant,benizi/vagrant,jberends/vagrant,bheuvel/vagrant,tjanez/vagrant,kamazee/vagrant,cgvarela/vagrant,blueyed/vagrant,PatOShea/vagrant,miguel250/vagrant,gpkfr/vagrant,carlosefr/vagrant,krig/vagrant,PatrickLang/vagrant,zsjohny/vagrant,gajdaw/vagrant,Chhed13/vagrant,benizi/vagrant,bdwyertech/vagrant,tknerr/vagrant,juiceinc/vagrant,carlosefr/vagrant,genome21/vagrant,johntron/vagrant,legal90/vagrant,gajdaw/vagrant,bshurts/vagrant,invernizzi-at-google/vagrant,ferventcoder/vagrant,pwnall/vagrant,MiLk/vagrant,apertoso/vagrant,crashlytics/vagrant,wangfakang/vagrant,jfchevrette/vagrant,tbarrongh/vagrant,kamazee/vagrant,crashlytics/vagrant,fnewberg/vagrant,benizi/vagrant,juiceinc/vagrant,kamazee/vagrant,mitchellh/vagrant,evverx/vagrant,doy/vagrant,wangfakang/vagrant,janek-warchol/vagrant,apertoso/vagrant,myrjola/vagrant,carlosefr/vagrant,fnewberg/vagrant,theist/vagrant,TheBigBear/vagrant,genome21/vagrant,cgvarela/vagrant,loren-osborn/vagrant