ENH: stats: Add the power_divergence function that generalizes the
chi-squared test statistic, and allow it to be used in chi2_contingency.
BUG: Change working dir when building extension.

Current working directory should be changed (to trusted one) when building
an extension so compiler accidentally won't pick up anything from (untrusted)
current directory.
BUG: optimize: fix epsfcn choice in minpack routines

An additional sqrt() was introduced in 703dc23 --- minpack takes the
sqrt internally, so it should not be done again.

The routines can still fail if the problem is badly scaled. The test is
here changed to be less badly scaled.  The correct choice of epsfcn is
problem-dependent and in general needs to be left to the user.

Fixes gh-2639
BUG: interpolate: ensure fitpack work arrays are aligned to double boundaries

gfortran on some optimization levels (-O3) assumes that double-precision
arrays are aligned in memory on sizeof(double) boundaries.

The fitpack_surfit routine failed to properly ensure this, which results
to crashes in some cases.

Fixes gh-1310
TST: interpolate: add regression test for gh-1310
Merge pull request #2696 from pv/fix-2639

BUG: optimize: fix epsfcn choice in minpack routines
Merge pull request #2559 from WarrenWeckesser/stats-chisquare-gtest

ENH: stats: Add the power_divergence function that generalizes the chi-squared test statistic, and allow it to be used in chi2_contingency.
Merge pull request #2698 from pv/fix-1310

 BUG: interpolate: ensure fitpack work arrays are aligned to double boundaries
BF: fix error saving zero entries in sparse matrix

I assumed obj.size was the same as np.prod(obj.shape), but this isn't so
for sparse matrices.  Fix and test.

Closes gh-2700
Merge pull request #2701 from matthew-brett/empty-sparse-fix

BUG: io: fix error saving zero entries in sparse matrix
MAINT: stats: Removed obfuscatory alias for 'vectorize' from distributions.py
RF: remove python 2.4 compatibility routine

arff was using a version of functools.partial for compatibility with
earlier pythons; remove now we depend on 2.6 or greater.
Merge pull request #2703 from matthew-brett/remove-functools-copy

RF: remove python 2.4 compatibility routine
DOC: Format DCT references the same way as HOWTO
Merge pull request #2705 from endolith/patch-3

DOC: Format DCT references the same way as HOWTO
Merge pull request #2660 from TomasTomecek/weave-build-cwd

BUG: Change working dir when building extension.
DOC: update 0.13.0 release notes.
DOC: Add scipy.sparse release notes.
DOC: add authors list to 0.13.0 release notes.

[ci skip]