pygit2 api reference

pygit2 api reference

#### Basic API (low-level)
* public libgit2 structs should be python objects (classes) - Example: git_repository => Repository()
* nameing convention: strip git_`struct_name`_* - Example: git_repository_config() => Repository.config()
* iterations should be implemented as a generator, if this is not possible we
  need to change libgit2 (other bindings will benefit from this as well)
* every method should map to one libgit2 function (exceptions are iterations)
* return values of methods
   * no lists use generators instead
   * no dictionaries use tuples or objects instead
   * no instantiation of objects use strings instead (important for generators)
     like sha1-hash for objects or names for references.


### High-Level API
* inheritance for every object
* no return value restrictions
* *pythonic*