Added doctests to Travis CI config
Added doctests to Travis CI config

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