add cassowary to .travis.yml
add cassowary to .travis.yml

ghisvail/vispy,ghisvail/vispy,michaelaye/vispy,Eric89GXL/vispy,michaelaye/vispy,michaelaye/vispy,drufat/vispy,drufat/vispy,Eric89GXL/vispy,ghisvail/vispy,drufat/vispy,Eric89GXL/vispy