Remove sith completely from the travis config.

.travis.yml

@@ -12,12 +12,9 @@ matrix:
   allow_failures:
     - python: pypy
     - env: TOXENV=cov
-    - env: TOXENV=sith
   include:
     - python: 3.5
       env: TOXENV=cov
-    - python: 3.5
-      env: TOXENV=sith
 install:
     - pip install --quiet tox-travis
 script:
@@ -27,4 +24,3 @@ after_script:
       pip install --quiet coveralls;
       coveralls;
       fi
-