Updated Composing_Data Tutorial
Updated Composing_Data Tutorial

Chart types now return value_dimensions only during
indexing, updated Tutorial accordingly.

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