added pj.plugin
Fix rbenv gems helper

Fixes gem versions with words (beta, pre) in the version or with
multiple installed versions not being highlighted, and compatibility
with GNU sed (related to robbyrussell/oh-my-zsh#1579).
Merge pull request #1583 from To1ne/pj.plugin

added pj.plugin
Merge pull request #1594 from jbhannah/rbenv-gems-fix

Fix rbenv gems helper
Merge branch 'master' into my-oh-my