ENH: stats: Some enhancements to the chisquare functions:

* Add the `axis` argument to stats.chisquare and stats.mstats.chisquare.
* Add the `ddof` argument to stats.mstats.chisquare.

Closes gh-2108 (trac #1583).
Modified the interpretation of the axis argument.

It is now the axis of the array resulting from broadcasting f_obs
and f_exp.

Also simplified the code a bit.
Update the docstring for mstats.chisquare, and change the casting of ddof in mstats.chisquare so the p value data type is correct when axis=None is used.
MAINT: stats: Improve chisquare docstrings, and add tests that compare stats.mstats.chisquare to stats.chisquare.
BUG: accept scalar mysize argument in signal.wiener

This makes it consistent with the documentation.
MAINT: fix non-integer usage in scipy.spatial.
MAINT: signal: clean up argument check in medfilt, medfilt2d, wiener
MAINT: fix non-integer usage in cluster and sparse.
MAINT: fix non-integer usage in io, interpolate and optimize.
MAINT: incorrect non-integer usage fixes: address comments @charris on pr-2533.
DOC: fix spatial.distance.squareform() argument/return parameters
MAINT: fix one more occurrence of np.prod inside reshape.
DOC: sparse: add link to Strongly Connected Components algorithm details.
MAINT: Removed extraneous #include <iostream>
PEP8: Fix errors in latest changes
PEP8: Fix errors in latest changes