add mock to travis.yml
add mock to travis.yml

pombredanne/dask,blaze/dask,mikegraham/dask,jakirkham/dask,gameduell/dask,dask/dask,jcrist/dask,jakirkham/dask,ContinuumIO/dask,vikhyat/dask,dask/dask,mrocklin/dask,mraspaud/dask,vikhyat/dask,mraspaud/dask,ContinuumIO/dask,cpcloud/dask,mrocklin/dask,cowlicks/dask,pombredanne/dask,jcrist/dask,blaze/dask,chrisbarber/dask