Remove themes doc travis test

git_ahead: Fix indicator override

Add chain theme to db

Fixes #186 by removing the PATH save/restore code from init.fish.

There isn't a single occurence where Oh My Fish code changes the
value of PATH variable.

Plugin code which changes the PATH variable should be aware of
the side-effects and manage PATHs correctly, avoiding duplication.

Tiny text improvements

some grammar/punctuation mistakes

bugfix: git_ahead no longer reports 'none' as 'ahead'

git_ahead: Rewrite code, fix ahead being reported as behind

registry: Add lolfish theme

registry: add hasanozgan/theme-lambda

Update theme docs (Themes.md)

registry: add rafaelrinaldi/theme-pure

This updates omf plugin to new architecture, moving
functions to `functions` directory. It also revamps the
separation of concerns between CLI and underlying
implementations, organizing them into directories,
whose are autoloaded in plugin startup.

Remove update instructions

Oh My Fish has been stable for many months, we no longer need the update
instructions on the main README.

Update package: fasd

Note for fasd:

Existing fasd plugin doesn't even work properly.

- No fasd_cd
- No default aliases (f, a, s, d, z, zz, ...)

So I forked it and totally rewrote it. Please consider it as different
plugin.

New theme: shellder

Shellder is a fork of agnoster, with smarter functionalities

Fix issue #197: quote OMF_PATH

Support omf- prefix for packages