Add support for installing Razor using OS packages

This introduces support for installing Razor using OS packages, along-side the
existing support for installing from git.  At the moment git remains the
default mechanism for installation, as we gradually move toward a more
standard release model.

Closes #91.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Merge pull request #92 from daniel-pittman/feature/master/91-support-packages-not-just-git

Add support for installing Razor using OS packages