Add an example of tarball source to the README

[dralley]

Unless I'm misunderstanding, it looks like this commit added the ability to source libraries from downloading a tarball over http instead of git. ff20311

It's not documented though. There should be an example doing this in the documentation along with any other supported source types.

(If that's not what the commit does -- the ability to source a library from a tarball at an arbitrary https URL would be really nice!)

[mattnite]

btw @dralley I'm working on a whole slew of improvements, I'll make sure this is covered in the new github pages soon

[mattnite]

ok FINALLY done, see the gyro.zzz section in the readme