add rbenv_execute helper for executing commands with rbenv enabled
add documentation for rbenv_execute
don't make ruby_version a required attribute on rbenv_execute
ruby_version, not rbenv_version
refactor helper functions in LWRPs into Chef::Mixin::Rbenv
use updated_by_last_action instead of inline resources in execute lwrp
Merge pull request #55 from RiotGames/execute-lwrp

Add execute LWRP