Caskfile: Move `phinze/cask` to `caskroom/cask`

Homebrew Cask has been moved to https://github.com/caskroom/homebrew-cask.

Closes #375.
.gitconfig: Make sure `go` never overrides branches

Closes #357. Thanks to @yukideluxe!
Brewfile: Install `hashpump`
.bash_prompt: Speed up the Git commands for the prompt

Fixes #227 and closes #380.
.bash_profile: Enable tab completion for `git` and `g`

Closes #197.
Brewfile: add instructions on how to change the default shell to Bash 4
Merge branch 'master' of https://github.com/mathiasbynens/dotfiles

# By Mathias Bynens (3) and others
# Via Mathias Bynens
* 'master' of https://github.com/mathiasbynens/dotfiles:
  Brewfile: add instructions on how to change the default shell to Bash 4
  .bash_profile: Enable tab completion for `git` and `g`
  .bash_prompt: Speed up the Git commands for the prompt
  Brewfile: Install `hashpump`
  .gitconfig: Make sure `go` never overrides branches
  Caskfile: Move `phinze/cask` to `caskroom/cask`