Huge amount of changes.

Backend::entries behaves as expected from a Dir.entries clone. It preserves the . and .. folders, which are navigable.

All backends are required to support paths with a leading slash, eg. '/root'.

It's now possible to get the name of a File/Dir.
Added a #directory? method.
Options for the Github backend are now directly passed to the gem.
Added tests for the Local backend.
Bumped version to 0.1.0.