Merge pull request #839 from infosiftr/mongo-3.1

Add mongo 3.1!

library/mongo

@@ -14,3 +14,6 @@
 3.0: git://github.com/docker-library/mongo@ab203d1904c8621d64e20683610cc238fa0a628b 3.0
 3: git://github.com/docker-library/mongo@ab203d1904c8621d64e20683610cc238fa0a628b 3.0
 latest: git://github.com/docker-library/mongo@ab203d1904c8621d64e20683610cc238fa0a628b 3.0
+
+3.1.4: git://github.com/docker-library/mongo@986013684d49e905152f5aa9ab5966fb13bf4211 3.1
+3.1: git://github.com/docker-library/mongo@986013684d49e905152f5aa9ab5966fb13bf4211 3.1