Package lydown using traveling ruby

[noteflakes]

Create a single file archive using traveling-ruby for osx and linux that includes:

• ruby 2.2.x
• lydown
• lilypond 2.19.x

A copy of lilypond will be bundled as part of the release (for each platform), and used exclusively from within lydown. lydown should be able to detect that a lilypond distribution is present inside its tree, and use it instead of looking for a lilypond installation.

In addition, we should prepare an installer script that could be downloaded and piped into bash, as used by tools like rvm.

So in the README file the installation instructions would include:

To install lydown issue the following command in your terminal:

curl -s http://git.io/p6oxyA | bash

The installer should script referenced by the URL should download the latest release for the user's platform, untar it, and install it in the relevant location (/.lydown). So the release's lib directory would be copied to /.lydown/lib, and the lydown binary would be at /.lydown/lib/app/bin/lydown. The installer will also create a symlink from /.lydown/lib/app/bin/lydown to ~/bin/lydown.