docs: working on the repository chapter (in progress)
docs: working on the repository chapter (continue)
fixed api changes for index.c

11d9f6b304 in libgit2 changed api for git_index_find()
variable renaming
added GIT_EINVALIDSPEC as error code and use error msg for expected failures
fix error message text
docs: document arguments in a few more methods
Revert mistake
Revert another mistake

Forgot the Python 3 changes to the API.
Add Python 3.3 to the list of supported versions
docs: finish first round on the repository chapter
docs: use PyDoc_STRVAR in the Object type
Define GETTER helper macro

To save typing, and increase coding consistency.
Define the METHOD macro and deploy it
travis: drop 3.1 since travis does not support it anymore
Use PyDoc_STRVAR in signature.c
Split treebuilder.c from tree.c
Use PyDoc_STRVAR in tree.c
Flat directory hierarchy: move src/pygit2/ to src/
Finish deploying PyDoc_STRVAR