Add a new official-image for mongo-express

* Add a new repo for mongo-express

mongo-express is a web-based MongoDB admin interfase written in Node.js, Express.js, and Bootstrap3.

library/mongo-express

@@ -0,0 +1,5 @@
+# maintainer: Nick Cox <[email protected]> (@knickers)
+
+0.30.43: git://github.com/mongo-express/mongo-express-docker@3290958fd1ff8218baad0ed85cf3e66123baab84
+0.30: git://github.com/mongo-express/mongo-express-docker@3290958fd1ff8218baad0ed85cf3e66123baab84
+latest: git://github.com/mongo-express/mongo-express-docker@3290958fd1ff8218baad0ed85cf3e66123baab84