Initial improvements for version 1.1
Nicer README
Fix time, timeout, deadcount. Do not add excluded links to backlog
Treat HTTP code 415 as not dead
Specify default for politeness in docs
Skip links containing spaces since urljoin don't handle them well

Would end up in infinite loop
Revert "Skip links containing spaces since urljoin don't handle them well"

This reverts commit d193a419f4f6e557588838914232761aaafe7705.
Handle some malformed links
Merge pull request #1 from janhoy/improvements

Several improvements