CLN/DEPR: html.border option -> display.html.border

[jreback]

xref #11784

html.border : int
    A ``border=value`` attribute is inserted in the ``<table>`` tag
    for the DataFrame HTML repr.
    [default: 1] [currently: 1]

should migrate this (by deprecation) and moving to a new option display.html.border to keep in-line with our namespacing.

[rdk1024]

I'll take a look at this during SciPy 2017 sprint weekend.