update commit function
add param to create_from_tree
correct log reference
Update symbolic.py
fix syntax error
Merge branch '0.3' of https://github.com/firm1/GitPython into firm1-0.3

Fixed most pressing issues, more to come in next commit as we introduced
a regression here.

Conflicts:
	git/objects/commit.py
	git/refs/log.py
	git/refs/symbolic.py
Assure API remains backwards compatible; update API docs
Merge branch 'firm1-0.3' into 0.3

This includes a few fixes to not break backwards compatiblity