Small changes for FooTable

Hey bradvin-

Awesome project, really well done.  I ran into a small issue while using this project and thought it might be good to contribute the changes I made.  

Essentially, I updated the code to take into account situations where the entire table is visible at a given breakpoint.  In this case, the detail row does not need to be added as it appears as an empty row.  

I ran into this use case while converting arbitrary tables (unknown table content)  to FooTables.

Thanks!
David