[patch] directory should not exist gives false-positive

[nruth]

Ran across this during use, it's an easy fix, just the wrong method being called (checked for file instead of directory).

Have added test coverage for it, but you may want to change how I've made it expect an error is raised. I saw you have a similar step already but it doesn't handle multiline step input (I think?) so added something simple instead of changing what's there already.

http://github.com/nruth/aruba/commit/ff158bb7ceb5512bdc252556e2ddafa88bc1d889
http://github.com/nruth/aruba/commits/dir_should_not_exist

[aslakhellesoy]

Attribution. Closed by 5a916f3.

[aslakhellesoy]

Merged. Thanks!