Make all git commands use the command prefix

This stops any fancy shenanigans related to the git.fish function.
Remove g function, add wrappers to git function

Now the function checks for gh (a Go-based Github wrapper) and Hub (a
Ruby-based Github wrapper) before falling back to plain old git, whereas
previously it only checked for hub.

gh is significantly faster than hub and provides the same functionality.
It's also written in Go, which is cool.
Add colors script from iTerm2 project page to bin
Remove fish_history from repo
Add .gitignore to ignore fish_history files
Remove config.symlink folder

There were duplicate folders. I'll have to address the bootstrap script
in the future, but for now it's driving me crazy.
Bugfixes for the ls command
Add managed-bin to fish_user_paths, add GOPATH

Also fixes a "==" vs "=" typo that was shown when I deleted the
non-canonical config.symlink folder.
Add new Vim bundles, remove unused ones

Gone:
- Airline, because of visual bugs
- Ctags, because I wasn't using it
- Greplace, because I wasn't using it
- tComment, because I wasn't using it

Added:
- vim-twig, for twig templates
- vim-tabular, for alignment issues
- vim-golang, for :Fmt and other goodies
- emmet-vim, because I missed it
Add new vim maps, filetypes, and the matchit macro

Visual:
- Color scheme is now set to a dark background

HTML / XML:
- macros/matchit has been enabled (switch between opening and closing
  tags with %)

Maps:
- Shortcuts to open file in new horizontal split has been fixed

- NERDTreeFind has been mapped to <leader>b

Hooks:
- gofmt (:Fmt) is now run on Go buffers after saving