Implement a basic "add to index" method.
Throw errors instead of returning a boolean.
Add documentation to the README.
Right, wrap lines at 80 characters to be consistent.
Free the git_index in all code paths.
Be cautious about NULL pointers from geterr_last().
Drop the `{}` around single-line if statements.
Put the * next to the type.

Consistency :point_up:
Merge pull request #25 from smashwilson/git-add

Support for git add.