brew.sh: Upgrade to PHP 5.6 (from 5.5)
brew.sh: Upgrade to PHP 5.6 (from 5.5)

PHP 5.5 caused a segmentation fault when trying to run `arc`, the `anarcist` command.

Ref. https://stackoverflow.com/a/33512066/96656.

Closes #617.

unity/dotfiles,unity/dotfiles,unity/dotfiles,unity/dotfiles