Allow launching from a launch file, use rospy.myargv() to remove ROS remapping arguments (#16)
* Use rospy.myargv() to remove ROS remapping arguments Required to allow launching from a launch file, otherwise get errors of the type:
```
System Message: WARNING/2 (<string>, line 7); backlink
Inline literal start-string without end-string.
System Message: WARNING/2 (<string>, line 7); backlink
Inline interpreted text or phrase reference start-string without end-string.
System Message: ERROR/3 (<string>, line 10)
Unexpected indentation.
usage: smach_viewer.py [-h] [-f]
smach_viewer.py: error: unrecognized arguments: __name:=smach_viewer
System Message: WARNING/2 (<string>, line 12)
Block quote ends without a blank line; unexpected unindent.
- ```
System Message: WARNING/2 (<string>, line 13); backlink
Inline literal start-string without end-string.
System Message: WARNING/2 (<string>, line 13); backlink
Inline interpreted text or phrase reference start-string without end-string.
- Solved 'Cannot start smach_viewer.py in launch file' problem #17