Support Berkshelf 3.0
Support Berkshelf 3.0

Berkshelf 3 replaces `Berksfile#install(path: path)` with `Berksfile#vendor(path)`

Signed-off-by: Seth Vargo <81550dbf04dfd8537ff7b3c014c6fbf86e0889dc@gmail.com>

375gnu/chefspec,Thalagyrt/chefspec,mcoolive/chefspec,jkeiser/chefspec,oldirty/chefspec,chefspec/chefspec,rsr5/chefspec,zuazo-forks/chefspec,shanethehat/chefspec,shanethehat/chefspec,lamont-granquist/chefspec,coderanger/chefspec,sethvargo/chefspec,Thalagyrt/chefspec,coderanger/chefspec,ranjib/chefspec,gsavage/chefspec,lamont-granquist/chefspec,chefspec/chefspec,h4ck3rm1k3/chefspec,sethvargo/chefspec,jtimberman/chefspec,jtimberman/chefspec,gsavage/chefspec,jkeiser/chefspec,aspiers/chefspec,bheuvel/chefspec,bheuvel/chefspec,mcoolive/chefspec,375gnu/chefspec,oldirty/chefspec,ranjib/chefspec,rsr5/chefspec,aspiers/chefspec,h4ck3rm1k3/chefspec