Added agg as default backend to default.mplstyle
Added agg as default backend to default.mplstyle

agg is the only backend fully supported in the notebook, since
other backends often require a display server such as XServer.
The user can swill switch backends using plt.switch_backend or
by supplying an alternative rc file

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