Fixes #119: rbenv has not released a final version with support to fish yet,...

Fixes #119: rbenv has not released a final version with support to fish yet, so for now, we are cloning the expected end-result

plugins/rbenv/rbenv.fish

+function rbenv
+  set command $argv[1]
+  set -e argv[1]
+
+  switch "$command"
+  case rehash shell
+    eval (rbenv "sh-$command" $argv)
+  case '*'
+    command rbenv "$command" $argv
+  end
+end
+