Updating branch of rosbridge_suite to 'develop' vs missing 'hydro-devel'

Hello!  Per this email:

http://lists.ros.org/pipermail/ros-users/2014-July/068820.html

There is no 'hydro-devel' branch in the rosbridge_suite repo so this is breaking when compiling from source in indigo.  Here is a small change to use the 'develop' branch instead, which allows the installation of rocon from source to succeed.

Thanks, Dylan