2014-10-21  Gerrit Holl  <gerrit.holl@utoronto.ca>:

	* pyatmlab/collocations.py:

	(CollocatedDataset):

	- Update error checking when primary can't be road

	(CollocationDescriber):

	- Do not try to extrapolate profiles, a prioris, or averaging kernels.
	Rather, when the three do not come on identical z-grids (i.e. for
	Tanso they don't), rather limit them all to the least common range.
	This is not absolute, as each profile may have its own z-grid.
	Therefore, cut them ALL off if more than a fraction (defaulting to
	0.5) at a certain level is outside the range.

	- Add a lot more comments explaining what I'm doing

	- Rename extend_common_grid to regrid_profiles, to more accurately
	describe what's going on.

	- Ensure that xa, xh, ak are all on the same z-grid prior to further
	processing

	- Some related bugfixes

	- Also show negative part of averaging kernels

	* pyatmlab/math.py:

	(regrid_ak):

	- Optionall cut away when z is outside teh old grid

	(apply_W_A):

	- Bugfix for location of pinv

	(smooth_profile):

	- Centralise actual work to smoothen a single profile (no
	vectorisation)

	* pyatmlab/tools.py(array_equal_with_equal_nans):

	- Like array_equal, but consider nans to be equal too.