extract out Source._url_and_domain() so WordPress.com can override id
add templates for webmention feature. #121
first pass at WordPress.com source and handlers. #121
extract lots of common webmention handling code out of publish.py into webmention.py
move expect_requests_get() to HandlerTest
minor noop tweak
first pass at blog webmention handler
blog webmentions: add test for source not found
blog webmentions: test domain translates to lowercase
blog webmentions: test target URL not found in source page
Moved original post discovery into bridgy and start doing reverse-lookup on the author's homepage
Store the results of posse-post-discovery in the database so they can be reused next time
Added a test for posse-post-discovery
Added a second test of posse-post-discovery to check behavior for multiple subsequent searches
Move original_post_discovery to its own module
Clean up original_post_discovery and associated tests with suggestions from Ryan
make models.SyndicatedPost a child of Source,
and only discover syndicated posts for one source at a time
Added new unit tests for original post discovery, mostly failure
modes. Also found and fixed a bug when h-feed has no h-entries.
Added three tests for more failure modes of original_post_discovery when requests get bad responses
Put posse-post-discovery into an NDB transaction to avoid race
conditions and duplicate SyndicatedPosts in the DB.

Additional stylistic tweaks to better match the style of the
project.