add more spectral functions and add new spectrum types to specgram im mlab, and cleanup window and detrend functions
add mlab tests for new spectrum types, window and detrend functions, and greatly expand existing tests
add more spectral plots and add new spectrum types to specgram in _axes
add tests for new spectrum types in _axes

even more axes tests

even even more axes

add test images for new spectrum plots
add CleanupTestCase, a unittest.TestCase with cleanup
increase performance of spectrum-related functions in mlab
modularize mlab tests
add demo for new spectral plot types
added information regarding new spectrum functions to CHANGELOG, whats_new, and api_changes
support axis in detrend_mean and minor fixups
more mlab tests
minor detrend_linear typo fix
change default NFFT and pad_to behavior
all mlab tests implemented
fix axes specgram figures
major mlab reworking
major mlab reworking tests
more mlab fixes 11
more mlab test fixes 11