Still need to handle row numbers correctly

Includes a hacky fix to skip ignored values and a temporary hardcoding
of the sheet profile.

normalize_row doesn't really need to dealw ith None
and theres a slightly more elegant way to calculate row numbers

According to  http://getbootstrap.com/css/#grid-intro
the proper way to get a full page layout is to use container-fluid
but a normal row, which has negative margin to undo the padding.

It's all very confusing; but this feels better than my first effort.

The container-fluid div appears to be superfluous in Bootstrap 3.1+
so I have removed it, and with it goes the 15px margin.

Google CSV to XLSX conversion results in dates being stored as date objects
rather than strings, so we need to cope with these

http://doughellmann.com/2012/11/12/the-performance-impact-of-using-dict-instead-of-in-cpython-2-7-2.html

Because not all sources might offer one