diff - use old fashioned iterators instead of callback based ones
memory allocation helper macros
diff - use new memory alloc macros
added assertAll and assertAny for test cases
diff - use generator instead of list
added test data for diff.find_similiar
fixed assert for diff.find_similiar test
pep8 fixes for setup.py

as reported by flake8
syntax highlighting for shell commands in sphinx
Update to changes in libgit2 concerning refs

Two methods have been drop:

- Repository.packall_references
- Reference.reload

The unit tests have been commented until we wrap the new reference
database from libgit2.
Merge remote-tracking branch 'esc/pep8/setup.py'
Merge remote-tracking branch 'esc/refactor/install_docs'
the extension compiles to _pygit2.so, so ignore that too
Merge branch 'master' into next
Implement the Repository mapping interface in Python

Add 'Repository.get' and low level 'Repository.git_object_lookup_prefix'