Updated the code that handles the "find" substitution argument to use the roslib python module rather than performing a system call to use rospack. The roslib module should be equivalent to what was being done before (but is more ideal from a maintenance perspective).
Updated the code that handles the "find" substitution argument to use the roslib python module rather than performing a system call to use rospack. The roslib module should be equivalent to what was being done before (but is more ideal from a maintenance perspective).

Also removed a couple of imports that are no longer being used.

bponsler/roslaunch_to_dot,bponsler/roslaunch_to_dot