Remove version alias for 2.1.0

After the 2.1.0 ruby will not use the patchlevel for 2.1+ releases.

The next release will be 2.1.1 so we don't need these aliases anymore.

See
https://github.com/sstephenson/ruby-build/commit/9e76ceb8bf772115e34c98802826da3884dd0b2c
and linked tweet.
Bump rbenv-build to v20131225.1
Merge pull request #72 from robbiegill/master

Bump rbenv-build to v20131225.1
Test against Ruby 2.0
Merge pull request #71 from boxen/rm-ruby-2-1

Remove version alias for 2.1.0
Bundler 1.5
Fix up local to properly require the right ruby version
Merge branch 'master' of https://github.com/boxen/puppet-ruby into fix-ruby-local-dep-ordering