Have Travis consider a pull request as passing as soon as required tests complete (#101)

Without this flag, the coverage test will hold up the status of the pull request.

Author: brettcannon

.travis.yml

@@ -20,6 +20,7 @@ env:
   - TESTING=cpython
 
 matrix:
+  fast_finish: true
   allow_failures:
     - env:
        - TESTING=coverage