Use SSL by default

As per https://dev.twitter.com/discussions/24239 and
https://twitter.com/perl_api/status/423210390684565504, the Twitter API now
requires SSL connections, so go use them.
squelch the legacy_list_api warnings
Kill the client-side tweet length check.

Just let the API do the check. Since we don't shorten URLs, our check
is way wrong anyways.
Implement :twitter-favorite
Merge pull request #160 from nelhage/twitter

Some misc twitter fixes and improvements