Fix memory leaks
Fixed typos
Removed C++ dependency for Cython.
BF: use simple multiplication instead of using exponentiation and pow to prevent the generated cpp code from calling pow (visual c gets confused because it doesnt know what version of pow to use)

Conflicts:
	dipy/tracking/streamlinespeed.pyx
Support list of streamlines having different shape
Merge pull request #411 from MarcCote/cython_memory_leaks

Fix memory leak in cython functions length and set_number_of_points