Merge pull request #2 from bit-pirate/master

makes script executable
refactored the rendering

It now uses subgraphs to render providers inside
interfaces, rather than using arrows. Also it adds
'(default)' to provider labels when they are the
default provider for its capability.
started extending the interactive graphics view

This will users to start/stop capabilities by
right clicking them.
Merge branch 'master' of https://github.com/osrf/rqt_capabilities
now able to view, start, and stop capabilities
Merge branch 'master' of https://github.com/osrf/rqt_capabilities into bit-pirate