Add cool off time constant to spec

* For some reason, 1 second is not enough on my mac
Give more time to functional test

* Incrementing a test file every second may be too tight for some
* machines.  Change this to 2 seconds.
Add support for multiple directories.

* Initial stab at multiple directory support.  User specifies multiple
* directories via -d command-line option, with each dir separated by
* a comma.
* Change Watcher to use MultiListener.
Add spec for multiple dirs
Merge branch 'multidir' of https://github.com/bsia/rerun

Conflicts:
	bin/rerun
clarify docs and tests for multiple dirs