This enables to directly launch a python file within any roslaunch file
Adapted by F.Keith for the extraction of the messages.

Fixes #22

Conflicts:

	include/dynamic_graph_bridge/ros_interpreter.hh
	src/ros_interpreter.cpp

  Launching an application in a roslaunch file may cause to send python
  command before the interpreter has read the prologue. This commit should fix
  this issue.