Tweaked RESOURCES.md

Formatted Stack Overflow with a space in between.
Capitalized Java in the Reddit link and removed the claim that it was official.
Removed Gitter room link
The documentation is official

docs/RESOURCES.md

 ## Useful Resources
 
-* [StackOverflow](http://stackoverflow.com/questions/tagged/java).
-* [The official java subreddit](https://www.reddit.com/r/java)
-* [The exercism/java Gitter room](https://gitter.im/exercism/java)
-* [Java documentation](https://docs.oracle.com/javase/8/)
+* [Stack Overflow](http://stackoverflow.com/questions/tagged/java).
+* [The Java subreddit](https://www.reddit.com/r/java)
+* [Official Java documentation](https://docs.oracle.com/javase/8/)
 * [Java Programming Books](https://github.com/vhf/free-programming-books/blob/master/free-programming-books.md#java)