DOC: harmonize correlate and convolve docstrings, list default option first, typos
MAINT: Use same error message for all 'valid' mode size checks, add same check to convolve2d
ENH: Use rfftn for real inputs in fftconvolve() to double the speed
DOC: move default option to the top of the list
DEP: Remove "old behavior" of fftconvolve, so it's the same as convolve/correlate, etc.
MAINT: Use a function to check "valid" mode shapes, remove check from convolve() since correlate() will handle it.
MAINT: combine fftconvolve lines into one,
add asarray and zero-rank check to correlate(), same as convolve(),
move same-rank check from convolve to correlate,
remove unnecessary mode check from correlate
BUG: fftn caused Floating point exception: reject empty arrays like numpy.fft.fftn
http://projects.scipy.org/scipy/ticket/1745
DOC: Add docstring to fftconvolve function
BUG: fftconvolve failed for n=1 inputs, due to ambiguity of irfftn
ENH: all convolve functions now accept array_like inputs
MAINT: fftconvolve behave same as convolve for zero-rank inputs
and less cryptic error for different rank inputs
TST: update tests for convolve/correlate/etc:
change tests so they work with "new behavior" of 'valid' and 'same' modes
add tests for empty arrays, single-element arrays, and zero-rank arrays
TST: Enable convolve2d tests, change test to match actual centering behavior of convolve2d() and convolve() in 'same' mode
MAINT: handle empty arrays better in fftconvolve.  Also some PEP8 changes.
TST: test consistency between various convolve/correlate functions.
MAINT: silence a ComplexWarning in sigtools._convolve2d.

Needs to be fixed properly at some point, but doesn't seem to affect results.
Merge branch 'fftconv' into merge-fftconv