taper: add a decorator for backwards compatibility and plenty of
DeprecationWarnings (one about future default behavior from 0.10.0
onwards)
taper: tests for backwards compatibility
taper: add some more tests and except another possible usage case
taper: for now leave Stream.taper() with *args/**kwargs, so it can't be
overseen for the next change with 0.10.0
taper: finish work on decorator (?!)
taper: remove an obsolete if-clause, thanks @trichter
add failing test
refactoring, however, I think we could delete this warning
enhance taper for the case 2*wlen==npts, maybe this is hypocritical, if you think so, please revert.
fix small error
pep8
fix warning

 what we want to test is the minimum constraint of all user added
 constraints
taper: override 'p' kwarg for cosine taper
change np.any to np.all
Merge pull request #650 from obspy/taper_backwards_compatibility

backwards compatible handling for Trace.taper()