TST: replace Python 2.7 by Python 3.3 in Travis CI config.
TST: replace Python 2.7 by Python 3.3 in Travis CI config.

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