Implement logarithmic polar grid

This grid has logarithmic spacing in radial direction and its azimuthal spacing
is constant with respect to the radius.
npart is signed and npartTotal is unsigned, fixed header.

Fixed the signedness of the header, don't know why npart isn't unsigned too.
Should file a bug...
Add more header fields.

This is in preperation for supporting more than 2**32 total particles per type,
which need setting the high byte of the particle numbers in the header.
Add support for header with more than 2**32 particles.

If there are more than 2**32 particles of one species total, the higher byte of
the number needs to be written to a seperate field. You still need to split the
file though, as n_part is only an int, so one file still only supports 2**32
particles.
Make the code work with python 3.

In Python 3 you can't concat binary strings directly. We use bytearrays
instead.
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.
Promote Box to a class and check parameters

A valid box must have equal dimensions in position and size. It also may not
have a negative size.

Fixes issue #23.
Add support for assert_less_equal and assert_greater_equal on Python 2.6
Fix monkey patching of assert_not_in.
Merge pull request #46 from Moredread/fix/monkey

Fix monkey patching of assert_not_in.
Merge pull request #41 from Moredread/feature/3d_random_grid

Conflicts:
	jelly/tests/nosetools.py
Merge branch 'master' into feature/box_class

Conflicts:
	jelly/tests/test_util.py
Merge branch 'master' into feature/logpolar

Conflicts:
	jelly/tests/test_util.py
Test get_type_of_cell function

This untested unit came up reviewing coverage reports.
Remove obsolete CustomObstacle

This had previously been used as a mock class but is no longer required for
testing.
Fix missing import of nose.tools.raises
Merge pull request #44 from aepsil0n/feature/box_class

Promote Box to a class and check parameters
Merge pull request #49 from aepsil0n/fix/remove_custom_obstacle

Remove obsolete CustomObstacle