DOC : Added doc for functions.qmf and functions.orthfilt
API : Thresholding functions merged into one
STY : PEP8 fixes in docstring
MAINT : Putting threshold function directly in pywt namespace
MAINT: fix some minor issues in thresholding and orthfilt().
Merge branch 'pr/49' into master.

Review at https://github.com/rgommers/pywt/pull/49

Note: this is the first change that breaks backwards compatibility
with PyWavelets!