remove bad quote from lambda arg to mapcar

  Thanks to jumpcannon for pointing this out.
remove `inf-ruby-keys' (which has been renamed)

According to https://github.com/technomancy/emacs-starter-kit/pull/145
this can just be removed, as the function should already be called if
inf-ruby is available.
Merge remote-tracking branch 'mainline/master' into my-change