Makes it possible to enable/disable table header with a boolean property...

I added a boolean to enable/disable table header (now enabled by default).
I hope this feature makes sense to you. Otherwise let me know how I could improve.
![table_header](https://cloud.githubusercontent.com/assets/24973/2531613/45334e24-b534-11e3-89c9-0b7d12551384.png)
In the screenshot above the first table has the header disabled and the table on the right has it enabled.
I forced the th input color to white (rather than dark), but there are probably other thing we could do to make it looks even nicer.