Updated and simplified setup.py
Updated and simplified setup.py

Now supporting install options holoviews[mpl,notebook,all]

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