listen -d can take multiple directories

[ideasasylum]

The listen script can now take multiple directories

I encountered the duplicate directories problem in my Rails project (a
vendor gem used symlinks) so the simplest solution was not to watch the
whole project directory (i.e., the default —directories option) but
just the directories I care about. That meant I needed to watch
multiple directories which listen supports but the listen script did
not.

This commit changes the -d option type from string to array and adds
the appropriate specs. The order of the options doesn’t matter: listen -d app spec -v -r is the same as listen -v -r -d app spec and then
directories app and spec are pass to Listen.to as an array

[coveralls]

Coverage decreased (-0.2%) to 98.76% when pulling 9c93b19 on ideasasylum:master into 2030bac on guard:master.

[e2]

Thank you very much - and for the tests!