Install casks via Caskfile

`brew bundle` can now be used for casks as well.

Closes #365.
Brewfile: Install GNU `sed`
Brewfile: Install some more useful tools
.functions: Make `gi` accept any number of arguments

Closes #367.
Brewfile: Install `xpdf`, if only for `pdfinfo`
.osx: Don’t reset the desktop wallpaper when resetting Launchpad

Files like `530142A0-6AEC-4921-A3A7-7C2B72FFF6E3.db` and `desktoppicture.db` exist in `~/Library/Application\ Support/Dock`, so let’s add a `-` with a wildcard `*` to both sides to ensure we don’t delete `desktoppicture.db` and reset the desktop wallpaper.

Closes #370.
Brewfile: Install `ucspi-tcp`, if only for `tcpserver`
Brewfile: Install PHP 5.5 with GMP support
.osx: Don’t show hidden files by default

Most of the time I don’t need it, and when I do, I can temporarily enable it using the `show` alias, and revert it using the `hide` alias.
Brewfile: Fix PHP 5.5 installation

Thanks to @interputed for the heads up: https://github.com/mathiasbynens/dotfiles/commit/a76db30d6529e41138009fe3dc67f21ba782496e#commitcomment-6200104
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
Brewfile: Install Node with npm

Ref. https://github.com/Homebrew/homebrew/pull/28075. Closes #362.
bootstrap.sh: Make `rsync` output numbers in a human-readable format

Closes #383.
Brewfile: Install BFG Repo-Cleaner
.curlrc: Set connection timeout to 60 seconds

This matches the setting in `.wgetrc`.