Implemented general object read/write and blob object
Fleshed out blob, tree, directory and entry
Implemented Tree#content. Refactored tree and blob to inherit from obj.
Implemented Tree.read and fixed Tree.build_from_dir
Create README
Fixed init command and gem source configuration.
Added ability to add objects to index
Added 'add' command to Repository
Using Thor for command line interface
Implemented basic commit
Repository#commit doesn't create commit object when index is empty