Instead of overwriting functions that use `exec fish` on test
environment, skip this call if the variable `CI` has been defined on the
running shell.

This Dockerfile creates an ubuntu machine with fish-shell and the
dependencies we use on our test suite installed.

It does not install Oh My Fish, which one might find weird (I do). Not
confident that this is the best approach, but it's the best I could find
at the moment.

Update pkg urls and add weather plugin

Faster loading

In order to support dependency between plugins a function called
`require` has been added.

Unnecessarily sourcing a `$plugin_name.fish` is affecting the loading
time.

Stash does not support --git-dir

Stash is a shell script that does not support `--git-dir`, not even on
latest versions. We need to use `git -C` which was only added on recent
versions of `git`.

`omf update` will fail in case omf need needs to run `git stash` and
git is not compatible.

Split custom "init.fish" into clearer "before.init.fish" and "init.fish"

add pastfish theme

Move $OMF_CONFIG variable to $OMF_PATH/init.fish

This PR sets the default value of `OMF_CONFIG` variable in
framework init.fish file. The variable can still be overridden by
the user by setting it on `~/.config/fish/config.fish file`.

This is in preparation to rewriting install script in plain fish,
which will ditch config template and stop replacing `config.fish`
contents in favor of just appending Oh My Fish startup.

Add test-generate-themes-doc.fish

* Run with Travis CI, if commits contain changes to `db/themes`
* When run; fail build if `docs/Themes.md` is no longer up-to-date

Add getopts pkg

Add kill-on-port pkg

Remove some pushd popd, using git --git-dir --work-tree

Add nelsonjchen theme to db

Travis: Base of travis test

Add tmux-zen plugin to db

README: add custom config file documentation

Remove src attribute from spacer image in the README

Moving and renaming install_fish.sh to travis_install_fish

Moving travis_* from tests to tools.

rename: fish_user_function/ -> functions_override/

renaming travis_test.fish to test_runner.fish