Add config for GNU screen and xsession.

The xsession config will run the awesome window manager on
startup.
Add config for zsh.
Add more aliases for git.
Install scala-mode for Emacs.
Add more file extensions to the Emacs config.

When opening a file with the given extension it should set
the appropriate mode (e.g. opening Gemfile will set ruby-mode).
Set javascript indent level to 2 spaces.
Remove cinnamon-settings-daemon from xinit.

Use gnome-settings-daemon instead. Not sure which one I should be
using though.