Added jump plugin
Removed realpath dependency
Actually, let's stick to builtins
Bug fixes
Additional gatekeeping
Two-space indentation
Merge remote-tracking branch 'upstream/master'

Merging in preparation of a rebase, per maintainer's request.
Bug fixes
Additional gatekeeping
Two-space indentation
Merge branch 'jump-plugin' of https://github.com/tripleplus/oh-my-fish into jump-plugin
Merge pull request #103 from tripleplus/jump-plugin

Jump plugin