Support numpy 1.9

Numpy 1.9 is out now. It does not include `__numpy_ufunc__`, so should be relatively easy to support. Am not quite sure what needs to be done to start testing: change `.travis.yml` and upload new version to travis?
@astrofrog?
Should be fine. I could wonder if you really want to return False instead of an error here or changing it in units as well might make sense... The thing is, at some point this would probably be a normal error, is that OK?