Switched .travis.yml to use latest IPython for all python versions
Switched .travis.yml to use latest IPython for all python versions

vascotenner/holoviews,mjabri/holoviews,vascotenner/holoviews,basnijholt/holoviews,ioam/holoviews,vascotenner/holoviews,ioam/holoviews,ioam/holoviews,mjabri/holoviews,basnijholt/holoviews,basnijholt/holoviews,mjabri/holoviews