Add PyInstaller build scripts

[tdryer]

Add build scripts for producing a PyInstaller distribution of hangups for Linux x86_64.

The result is an archive containing hangups that should work on any Linux distribution with glibc >= 2.12 (CentOS 6+, Ubuntu 12.04+, or similar). No Python required!

Sample: http://tomdryer.com/hangups/hangups-0.4.2-linux-x86_64.tar.gz

tar xf hangups-0.4.2-linux-x86_64.tar.gz
hangups-0.4.2-linux-x86_64/hangups