pylint cleanup: unused imports and old-style exceptions
add testing environment for development versions of w3lib and queuelib
restored import *, added comment
Merge pull request #430 from alexanderlukanin13/cleanup

pylint cleanup: unused imports and old-style exceptions
PEP8 improvements

* Space lines around classes/functions.
* Space in inline comments.
* Remove redundant backslash between brackets.
Removed reference to URL in crawl command as it's no longer supported.
DOCS removed .tld suffix for spider names for the sake of consistency.
Merge pull request #432 from darkrho/crawl-url

Removed URL reference in crawl command and .tld suffix in docs for spider names
simplified description of crawl command