rename bash -> sh, remove bash installation from bootstrap
consistent install_* in appropriate files
move git clone to 05-git
extract join_if_list, use it in sh_output too
add brew-cask support
fix sudo_sh for quotes
add options to brew and brew-cask
Fix singleton variable warning in test.
Strip prolog header from test output.
Fix the bootstrap instructions.

It had broken due to GitHub serving a 301 which we weren't following.
Merge pull request #13 from myfreeweb/master

brew-cask support, bash -> sh, etc.
Update on any cask package install.
Abstract out symlinking predicates.
add handling for packages by yaourt, based on that of pacman
yaourt uses pacman, so should depend on pacman-update, not its own
yaourt should not be run as root: it uses sudo as necesary itself
pacman, yaourt should only check for native, foreign packages respectively
brew-update should depend on brew, which should depend on osx
python can be installed with pacman
python: assume the equivalent of build-essential has been met