added support for in source python usage
added support for in source python usage

ros/catkin,thaddeustaylor/catkin,scpeters/catkin,asmodehn/catkin,thaddeustaylor/catkin,scpeters/catkin,scpeters/catkin,wkentaro/catkin,jack-oquin/catkin,shyamalschandra/catkin,asmodehn/catkin,jack-oquin/catkin,wkentaro/catkin,beni55/catkin,meyerj/catkin,shyamalschandra/catkin,meyerj/catkin,shyamalschandra/catkin,thaddeustaylor/catkin,beni55/catkin,harmishhk/catkin,wkentaro/catkin,harmishhk/catkin,ros/catkin,harmishhk/catkin,meyerj/catkin,ros/catkin,asmodehn/catkin,jack-oquin/catkin,beni55/catkin