docs: no need to @-mention author in twitter replies, bridgy does that for you now
during blog signup, check for webmention endpoint and Disqus (only for tumblr)

if they're not found, show instructions for setting them up on the user page
drop unnecessary requests.get allow_redirects=True kwarg

it's the default, and future proofing is silly. (this one's for you, @kylewm! :P)