Don't install gevent on python3.3; gevent no longer supports 3.3.

.travis.yml

@@ -21,6 +21,8 @@ matrix:
   include:
     - python: pypy
       env: TEST_REQUIRE=fastimport
+    - python: 3.3:
+      env: TEST_REQUIRE=fastimport
 
 install:
   - travis_retry pip install -U pip coverage codecov flake8 $TEST_REQUIRE