Don't install numba with numpy 1.13 (#2479)
Don't install numba with numpy 1.13 (#2479)

Currently numba is incompatible with numpy 1.13. Fix the travis install
script to not install numba in this case. Also clean up some cruft that
had accumulated.
dask/dask,mrocklin/dask,mrocklin/dask,blaze/dask,ContinuumIO/dask,blaze/dask,jcrist/dask,jakirkham/dask,jcrist/dask,jakirkham/dask,ContinuumIO/dask,dask/dask