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?
@seberg, @juliantaylor - I think it is indeed fine as is, even if strictly we do not have to return `False` on the `UnitsError` (since two `NotImplemented` will result in `False` just as well). Your comments, though, suggest it may be more logical to catch the `DeprecationWarning` for numpy 1.9 in our test suite rather than in our main code, and leave the main code the same until the exceptions are really passed on. On the other hand, now at least we should be ready for that... Possibly, it should be a combination, i.e., keep the `UnitsError` and `TypeError` checks, but move `DeprecationWarning` to the tests.  But then, as it is, anyone else running astropy with warnings visible will not be bothered by these.  @astrofrog - what do you think?