1 - Fixed typo in docs.
2 - Removed commented out code.
3 - Removed redundant code (factor_symbol in
    ga.py).
4 - Added special cases of multiplication by
    zero in mul, dot, and wedge of ga.py.
5 - Fixed return error in grads() in ga.py.
6 - Moved imports of IPython functions to
    where they are imported only if IPython
    is being used. (Thanks to Julien
    deKozak for 1, 5, and 6).