Update vagrant completion with "plugin" subcommand

This subcommand was added in Vagrant 1.1.
Update ack to work with version 2+
Use cache-policy for _gem
Check GEM_HOME to compare recency
(gem) Add open command
Added completion for ralio, a rally client
Remove superfluous create/delete options
Specify the help text for the -t option
(ack) handle ack version string containing commit sha1
separate branches
Separate values for bundle help
Removed reference to git flow
Add mina completion.
Merge pull request #136 from markcornick/vagrant_plugin

Update vagrant completion with "plugin" subcommand
Merge pull request #137 from zhaocai/feature/_gem

Use cache-policy for _gem
Merge pull request #138 from zhaocai/feature/_ack

Update ack to work with version 2+
Merge pull request #140 from peteryates/master

Added completion for Ralio
Merge pull request #141 from luolimao/yaourt

Added new Yaourt options
Merge pull request #144 from graywh/patch-1

Separate values for bundle help
Merge pull request #145 from mitukiii/mina

Add mina completion.