TST: remove fudgy ujson test #4223
Removed ambiguous ujson test, see #4223, #4186.

Hmm looks like there is an ongoing build issue (for numpy `ImportError: libatlas.so.3gf: cannot open shared object file: No such file or directory`). 

Let me know if I need to push again later to re-run travis...
 you should rebase against master to update 

going to merge this in any event

thanks!
 woops, forgot to rebase before pushing, my bad. thanks @jreback!
