Add Support for Data Table Scrolling

[kwilloughby]

I'd like to add support for data table scrolling. Below is an example. In this example the table header remains visible at all times. The example also shows horizontal scrolling because the table is too wide.

[kwilloughby]

@pixelprodotco for visibility.

[interactivellama]

I know how to do this is style CSS hacks. Is there's an SLDS way / pattern to do it?

Review #255 for more background on this issue.