Material-table: Fixed thead, scrollable tbody

[timrchavez]

Is your feature request related to a problem? Please describe.
There are times when you don't want to use paging, but have more rows than screen real estate. In this case, it would be nice to keep the header in view so the user can maintain context and quickly associate column values with column types.

Describe the solution you'd like
It would be nice to be able to keep the thead fixed while allowing tbody to be scrollable with a prop setting.

[mbrn]

I will merge #313 asap.

[timrchavez]

Thanks for being so responsive!!

[mbrn]

This is done. I added maxBodyHeight to options.