Dvreed77/palette docs

I have added some documentation to list all the palettes.  The HTML was generated with the code below and probably should be generated automatically during the building process.  

    from bokeh import palettes as pl

    s = "<table>"
    for i, (k, v) in enumerate(pl.brewer.iteritems()):
        for k1, v1 in v.iteritems():
            s += "<tr><td height='20px' width='80px' style='font-size: 12px'>%s</td>" % (k+str(k1))
            for j, a in enumerate(v1):
                s += '<td height="20px" width="20px" style="background-color:%s">' % a
            s += "</tr>"
    s += "</table>"