Implemented 3D version of MonteCarloGrid + fixes

Improved documentation, fixed use of the box API and improved formatting.

TODO: Test the MonteCarloGrids
Added TODO to doc, reminding to test the code
Add tests for Monte Carlo grids.

Testing if vectors are in the given box and if the correct number of vectors are
yielded.
Add support for assert_less_equal and assert_greater_equal on Python 2.6
Merge pull request #41 from Moredread/feature/3d_random_grid

Conflicts:
	jelly/tests/nosetools.py