ENH: Add canonical representation for lti objects
BF: ensure ordering of OrderedDict keys

Test was failing because of unexpected key ordering - closes gh-2503.
MAINT: stats: remove unused '**kwds' from the definition of kstest()
MAINT: remove the file 'TEST_COMMIT'
Merge pull request #2506 from WarrenWeckesser/maint-rm-test-commit

MAINT: remove the file 'TEST_COMMIT'
Merge pull request #2505 from matthew-brett/mat-dict-py33-fixes

BF: ensure ordering of OrderedDict keys
ENH: allow nc <=0 in non-central t-distribution.  Closes issue gh-2402.

For the non-centrality parameter nc negative values and zero should be allowed.
Therefore an _argcheck added which only restricts degrees of freedom df to
positive values.
TST: add test for broadcasting in stats.nct distribution.
Merge pull request #2457 from SytseK/non_central_t_branch

See https://github.com/scipy/scipy/pull/2457
DOC: add note about using fftshift, change Nyquist sign.

fftfreq and fftshift consider the Nyquist frequency to be negative:

In : fftshift(fftfreq(8, 1/8))
Out: array([-4., -3., -2., -1.,  0.,  1.,  2.,  3.])
Merge pull request #2454 from endolith/ltisys_changes

ENH: Add canonical representation for lti objects