remove needless tp_getattro entries
use PyObject_New() for object instanziation
Use basic types for objects and grouped types into groups
use utils helper macros/functions through the whole lib

* use to_unicode()/to_unicode_n() for creation of unicode strings
* main support switch to python3 instead of python2 (provide defines for python2)
Repository_read().data should be binary data
reactivated TreeBuilder test
fixed non working test for config.set_multivar()
added missing unittest.main() for tests_remote.py
Make bug #196 to show up with Python 2
Fix import (#196) using relative imports
Merge branch 'master' into next

Conflicts:
	include/pygit2/types.h
	src/oid.c