Fix check_paths definition for pep8tool

[chocoelho]

See #257 (comment), and check this fix against this repo.

Seems like the way check_paths was defined it excluded some paths before checking the full path of folders, leaving some of them out of the inspection depending on the given path.

[coveralls]

Coverage decreased (-0.01%) to 77.688% when pulling bc5663d on vintasoftware:fix-pep8-filepath into 4cc89a3 on PyCQA:develop.

[coveralls]

Coverage decreased (-0.01%) to 77.688% when pulling 685b24b on vintasoftware:fix-pep8-filepath into 264d0ad on PyCQA:develop.

[chocoelho]

@carlio just to give some context on what's happening here, prior to this change:

path_a/
---- path_b/
-------- path_c/

If prospector is ran at the current folder (say path_a) prospector ., path_c won't be listed among found files/folders for pep8 tool so it won't throw any warnings/errors if any exists and this folder (path_c) will only show up if prospector is ran explicitly against path_a, e.g. prospector path_a. What I found is that the removed line would skip listing path_c, because it'd be considered as already inside check_pathsvariable (checked that by debugging).

[carlio]

Well I absolutely can't remember the reason for that initial iteration so sure :-)