cleanup README (apache#3037)

Author: Neng Lu

README.md

@@ -17,16 +17,10 @@ Heron is realtime analytics platform developed by Twitter.  It has a wide array
  * Python 2.7
  * Bazel latest
 
-
 ## Contact
 
 #### Mailing lists
 
-Heron User Google Group: [[email protected]](https://groups.google.com/forum/#!forum/heron-users)
-
-Heron on Twitter: [@heronstreaming](https://twitter.com/heronstreaming)
-
-
 | Name                                                                      | Scope                           |                                                                |                                                                    |                                                                           |
 |:--------------------------------------------------------------------------|:--------------------------------|:---------------------------------------------------------------|:-------------------------------------------------------------------|:--------------------------------------------------------------------------|
 | [[email protected]](mailto:[email protected]) | User-related discussions        | [Subscribe](mailto:[email protected])  | [Unsubscribe](mailto:[email protected])  | [Archives](http://mail-archives.apache.org/mod_mbox/incubator-heron-user/)|
@@ -40,6 +34,8 @@ Heron on Twitter: [@heronstreaming](https://twitter.com/heronstreaming)
 
 [Bay Area Heron Meetup](https://www.meetup.com/Apache-Heron-Bay-Area), *We meet on Third Monday of Every Month in Palo Alto.*
 
+#### Twitter
+Heron on Twitter: [@heronstreaming](https://twitter.com/heronstreaming)
 
 ## For more information: