Accept list of paths in 'path' arg.

This adds the behavior of splitting the path positional argument on colons then
processing each resulting string the same way that the path was being processed
previous to this commit.

* Adds a unit test to validate correct `path` parsing.
* Adds a unit test to validate correct `path` parsing in the recursive case.
* Documents the new behavior.

Change-Id: I0f465e02077569352cd276a8366ead5bab0eb117