new ereporter exception
publish preview: don't choke on likes, etc which don't have content of their own

@peterwilson just fyi, this fixes the bug you hit with previewing a twitter favorite
outgoing blog webmentions: follow redirects *before* filtering out self links
canonicalize facebook /photo.php?fbid=ID syndication urls to /USER_ID/posts/ID

for #189
switch from html2text/html2text to Alir3z4/html2text, part 1/2

for #302
switch from html2text/html2text to Alir3z4/html2text, part 2/2

fixes #302
set twitter app key and secret in tests. fixes #302
when normalizing photo post ids to fb object id, also normalize url. for #189
minor noop test refactoring
end to end test with syndication URL with FB object id instead of post id

(maybe but who knows for sure) fixes #189. cc @kylewm. i won't believe it until i see it actually work in production.

now i just need to find a picture i want to post to FB... :P
facebook: add support for event comments. for #49
tweak "response changed" logging
facebook: ask for event likes.

this is aspirational - FB doesn't actually send them - but it should work if/when they do. details in https://github.com/snarfed/bridgy/issues/49#issuecomment-60406365
merge commments and likes from FB photo and photo post objects

yet more work to handle FB's awful data model for photo posts. kind of for #189...kind of.
fail fast if we see a facebook id with a colon in it. fixes #305
minor bug fix for cc02b9762c387e5f5d0ce10ceb6b1179fb3fb08a
tweak blogger and ereporter error exceptions
noop comment tweak: add blogger api doc links
add RSVP screencast to about page
script that generated the graphs in https://snarfed.org/2014-11-06_happy-1000th-bridgy