Added new libraries to README

@@ -60,6 +60,7 @@ To see a more sophisticated Ring app, run:
 * `ring.middleware.file`: Serve static files out of a public directory.
 * `ring.middleware.static`: Serve static files with specified prefixes out of a public directory.
 * `ring.middleware.file-info`: Augment response headers with info about File responses.
+* `ring.middleware.content-type`: Augment response headers with a content-type based on the file extension.
 * `ring.middleware.params`: Parse query and form params.
 * `ring.middleware.multipart-params`: Parse multipart params.
 * `ring.middleware.keyword-params`: Convert string param keys to keywords.
@@ -68,6 +69,9 @@ To see a more sophisticated Ring app, run:
 * `ring.middleware.session`: Manage user sessions. Memory and cookie session stores are available by default.
 * `ring.middleware.flash`: Adds flash message support to sessions.
 * `ring.util.response`: Generate Ring responses.
+* `ring.util.codec`: Encode and decode string data.
+* `ring.util.mime-type`: Guess the mime-type from a file extension.
+
 
 ### ring-devel