Update documentation for rebase

The release/upstream branches no longer exist; everything is now in
develop. This fixes #56.

INSTALL.md

@@ -18,12 +18,11 @@ $ echo $JAVA_HOME
 $
 ```
 
-Now you can clone a copy of this repository and switch to the `release` branch if it is not automatically checked out:
+Now you can clone a copy of this repository:
 
 ```
 $ git clone git://github.com/Libresonic/libresonic.git
 $ cd libresonic
-$ git checkout release
 $
 ```