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