Update README.txt

Removed spaces from the grun alias so copy and paste people will not get an error.
Merge pull request #149 from abrown28/master

Removed extraneous spaces from the alias grun command
don't call process() if args aren't specified
added Dave Parfitt to contributors.txt
Merge pull request #151 from metadave/dip_check_args

don't call process() if args aren't specified
Additional IntervalSet unit test (catches underlying cause of #153)
Fix IntervalSet.add when multiple merges are required