Merge pull request #5 from kartikprabhu/master

improved in_reply_to parsing
add json mf2 and activitystreams test data for embedded in-reply-to parsing

just in case you're curious, @kartikprabhu, this is what the rest of the test data looks like. thanks again for the contribution!
style tweaks for new mf2 in-reply-to parsing
Facebook.create() doesn't support shares
add ssl library to app.yamls
add <meta charset="utf-8"> to html output. thanks @kevinmarks!
update mf2py
twitter create: handle trailing slashes on URLs

fixes snarfed/bridgy#106
facebook create: support photo urls. fixes #103
optimize cache usage in get_activities() to one get_multi() and one set_multi()

for snarfed/bridgy#110
update webutil
twitter create: support photo urls. fixes snarfed/bridgy#105
update mf2py
link to original post in publish previews of replies, likes, etc

fixes snarfed/bridgy#111
Facebook publish: put original post link in custom "See Original" action link

fixes snarfed/bridgy#100
update webutil
readme: update submodule init command, move related work to bottom
don't log spurious error in Facebook.base_object() when there's no base object
fix cache gating in G+ and Twitter get_activities()
switch to twitter's link shortening behavior