release: version 0.1.3

- Optimized `fry rubies`, before it was slowed down by the amount of
  rubies you had installed.
- Switch from `PATH` to `fish_user_paths`, this allows further control
  and visibility into your paths. You might not want to have the ruby
  path very first etc.
- Add config option for `prepend` path. In case you would like to have
  identical behaviour to the previous implementation (if you are using
  `fish_user_paths` for something).
- Introduce `fry env` that is a helper function to output a POSIX
  compatible PATH export.
- Rubinius gems path was moved in front of the ruby path