Change to allow egg launching from a URI.  Tested with
bin/nosetests ion/agents/instrument/test/test_driver_process.py
Also will work with ion/services/sa/test/test_driver_egg.py once that code is brought in from Ian.
removed trailing slash in repo base per swarbhanu.
Merge pull request #489 from unwin/master

launch driver process from egg working.

Smoke tests are passing on dev machines.