Update mongo with simpler Dockerfile and smaller size

library/mongo

@@ -1,5 +1,5 @@
 # maintainer: InfoSiftr <[email protected]> (@infosiftr)
 
-latest: git://github.com/docker-library/mongo@e887f95172218b480dac20f0bc28a3291aa59a10
-2.6: git://github.com/docker-library/mongo@e887f95172218b480dac20f0bc28a3291aa59a10
-2.6.1: git://github.com/docker-library/mongo@e887f95172218b480dac20f0bc28a3291aa59a10
+latest: git://github.com/docker-library/mongo@f3327851aa89d923465a1b361f5d5a3d4139342c
+2.6: git://github.com/docker-library/mongo@f3327851aa89d923465a1b361f5d5a3d4139342c
+2.6.1: git://github.com/docker-library/mongo@f3327851aa89d923465a1b361f5d5a3d4139342c