Removes mongodb v2.6.11 from test suite (#2619)

Author: flovilmart

.travis.yml

@@ -16,11 +16,10 @@ env:
   - COVERAGE_OPTION='./node_modules/.bin/istanbul cover'
   matrix:
   - PARSE_SERVER_TEST_DB=postgres
-  - MONGODB_VERSION=2.6.11
   - MONGODB_VERSION=3.0.8
   - MONGODB_VERSION=3.2.6
 matrix:
-  fast_finish: true,
+  fast_finish: true
 branches:
   only:
   - master