MAINT: Make dwt2 use dwtn.
MAINT: Make dwt2 use dwtn.

This replaces dwt2 with dwtn under the hood. The only thing done is to
check the number of dimensions in the input and unpack the result
dictionary into a tuple.

eriol/pywt,rgommers/pywt,aaren/pywt,kwohlfahrt/pywt,aaren/pywt,PyWavelets/pywt,michelp/pywt,grlee77/pywt,rgommers/pywt,michelp/pywt,aaren/pywt,rgommers/pywt,PyWavelets/pywt,rgommers/pywt,eriol/pywt,eriol/pywt,michelp/pywt,kwohlfahrt/pywt,grlee77/pywt,kwohlfahrt/pywt