DOC Improvements to documentation & demos
RFCT Always use safe form of SAFE_SWITCH_ON...

Removed the non-safe SWITCH_ON... and the last argument to
SAFE_SWITCH_ON_.. It was always true, except for a couple of cases,
which I changed to be true. Then, I removed the argument and made the
behaviour be exactly like the one when true was given in the previous
version.
ENH Add `max_iter` arg to SLIC
DOC List of possible improvements to mahotas
DOC Improve tasks page
RFCT Use np.log2 for log-base 2
DOC Mention tutorials as possible improvement
DOC Better error message
ENH Add haralick_features function
MIN Add ``out`` parameter where it was missing

``cerode`` was still using ``output`` (instead of ``out``)! Other
functions did have it, but undocumented.
ENH Add m parameter to SLIC
DOC Update internals. Mention release schedule
MIN Whitespace fix in code
MIN Better error messages
BUG fix erode(f, np.zeros())

Amazing how this bug stuck around for such a long time
ENH Special case erode()/dilate() for speed

This is not the best yet because the boundary conditions changed. I
actually prefer these boundary conditions, but it is not trivial to
change the older dilate() code.
TST Test internal._check_3
TST More testing of mahotas.colors
TST Test error checking in texture.cooccurence
MIN Fix long standing warning in TAS

The previous code worked when numpy was set to raise exception on
numeric errors, not otherwise