Prevent black space after last filter is removed

Fixes this blank space which is left after the last filter is removed:
![filters](https://cloud.githubusercontent.com/assets/992533/3723624/3ed7b20c-1675-11e4-8883-868e503391a8.png)

The ```table.filters:not(:empty)``` styling does not work because tbody is left over after all the filters are removed. This fix also removes tbody when there are no filters left.