Prefer gawk over awk if both are available.
Merge pull request #581 from LawnGnome/solaris-gawk

Prefer gawk over awk if both are available.

Fixes rbenv-help on Solaris 11.1
Get rid of explicit exit in fish branch of `rbenv-init`

Allows for code to be added to the end of the script which will not
mysteriously fail to run for fish shell.
Updated two rbenv plugins.
Merge remote-tracking branch 'sstephenson/master'

* sstephenson/master:
  Get rid of explicit exit in fish branch of `rbenv-init`
  Prefer gawk over awk if both are available.