Added lint to .travis
Install puppet-lint as gem instead of package
Added ruby repo to .travis
Revert "Added ruby repo to .travis"

This reverts commit 067e7940968c01e3818c0096d1836ac12b5f909f.
Added ruby-version to make it use system ruby
Changed to gem version of puppet lint
Removed .ruby-version
Revert "Removed .ruby-version"

This reverts commit 3463fef231869f7234281d34f9a6c8368ef0fed3.