BLD: use pip for pywavelets, fix numpy downgrading in travis
BLD: use pip for pywavelets, fix numpy downgrading in travis

PyWavelets now provide wheels so we can use pip without worries. This also removes the implicit Numpy installation from the `conda create` build step, which often used the (for us) broken 1.14.2.

To avoid installation of a lower NumPy version by the `conda install` of `pyfftw`, the `--no-deps` flag is added there.
odlgroup/odl,kohr-h/odl,kohr-h/odl,odlgroup/odl