Use latest mongo in each series

Author: durran

.travis.yml

@@ -21,9 +21,9 @@ env:
     - CI="travis"
     - JRUBY_OPTS="--server -J-Xms512m -J-Xmx1024m"
   matrix:
-    - MONGODB=2.4.12
-    - MONGODB=2.6.7
-    - MONGODB=3.0.0
+    - MONGODB=2.4.13
+    - MONGODB=2.6.9
+    - MONGODB=3.0.1
 
 before_script:
   - wget http://fastdl.mongodb.org/linux/mongodb-linux-x86_64-${MONGODB}.tgz -O /tmp/mongodb.tgz