ENH: signal: spectral: Add periodogram and welch functions
BUG: signal: spectral: fix various bugs in periodogram and welch.

1. various off by 1 issues in dealing with the output of fftpack.rfft.
2. the DC and nfft/2 points shouldn't be scaled by 2 for 'onesided'
3. error in computing frequency axis in 'onesided'

The output of welch exactly matches matplotlib.mlab.psd for both even
and odd length  one-sided spectra and even length two-sided spectra of
real data.  For odd length two-sided spectra of real data, welch matches
the spectrum but matplotlib.mlab.psd return an incorrect frequcny axis.
BUG: signal: spectral: Fix bug introduced in last commit

We want fftbins=True in signal.get_window.  matplotlib.mlab.psd
effectively uses fftbin=False since this option doesn't exist in numpy.
Swapped this in to do some testing.
ENH: signal: spectral: Support detrending in welch.
MAINT: signal:  update binary attrib on _spectral.c

This marking was lost when the file was renamed.
BUG: signal: welch: call detrend instead of doing it by hand.

To support detending via a polynomial, we could extend detrend.
TST: signal: add test for welch

Also, fix bug in welch.
TST: signal: add tests for periodogram
BUG: signal: spectral: address review comments
FIX: signal: spectral: implement periodogram in terms of welch

Also finish addressing comments.
STY: signal: spectal: 80 character lines.
MAINT: Fix deprecated non-integer index to numpy arrays
Merge pull request #390 from jseabold/fix-int-idx

MAINT: Fix deprecated non-integer index to numpy arrays
BUG: update py3tool for spectral.so rename
BUG: fix py3k issue in signal.spectral
MAINT: signal.spectral: fix integer division and some formatting stuff.
Fixed a bug in scipy.stats.mstats.kurtosis() that caused a ValueError to be thrown when bias=False. In the same context, fixed a TypeError that was being thrown for one-dimensional input where all elements are masked.

Appropriate tests have been added to the testing suite for the function.

Fixed a bug in scipy.stats.mstats.kurtosis() that caused a ValueError to be
thrown when bias=False. In the same context, fixed a TypeError that was being
thrown for one-dimensional input where all elements are masked.

Appropriate tests have been added to the testing suite for the function.

Relates to ticket: http://projects.scipy.org/scipy/ticket/1798
MAINT: suppress warning in scipy.stats.kurtosis.

Happens for 1-D input having a second moment equal to zero (i.e. m2==0).
TST: add mstats.kurtosis test case, fix some formatting and minor style issues.
Merge branch 'pull-391-mstats' into master.  Closes #1798.

Reviewed at https://github.com/scipy/scipy/pull/391