Add support for tags

[benhocker]

Getting this error when checking my Puppetfile:

r10kdiff.rb:9:in `eval': unknown keyword: tag (ArgumentError)

According to the r10k documentation, tags are supported:

When a module is installed using :tag or :commit, r10k assumes that the given object is a tag or commit and can do some optimizations around fetching the object. If the tag or commit is already available r10k will skip network operations when updating the repo, which can speed up install times.

# Install puppetlabs/apache and pin to the '0.9.0' tag
mod 'apache',
  :git => 'https://github.com/puppetlabs/puppetlabs-apache',
  :tag => '0.9.0'

[dcosson]

Is this addressed by #2 ?

[benhocker]

Yes. Thanks!

[aj-jester]

It only sort of addresses it. It fixes the ArgumentError but the tag value is not being used as ref in #2, #3 fixes that.