remove tests against np1.9.  I can't get radio_beam to install locally at all in my np1.9 environment because of this: ``` error: numpy 1.9.3 is installed but numpy>=1.10.0 is required by set(['astropy']) ``` Since np19 is super old anyway, I don't think we need to keep supporting it.
remove tests against np1.9.  I can't get radio_beam to install locally
at all in my np1.9 environment because of this:
```
error: numpy 1.9.3 is installed but numpy>=1.10.0 is required by set(['astropy'])
```
Since np19 is super old anyway, I don't think we need to keep supporting
it.

e-koch/spectral-cube,low-sky/spectral-cube,jzuhone/spectral-cube,radio-astro-tools/spectral-cube,keflavich/spectral-cube