CHANGELOG: Update with summaries of recent changes

CHANGELOG: Update with summaries of recent changes

This documents the following changes:
5fd97a2 Add George Saunders to __contributors__
bd7b7ca error: Don't explicitly store server in SMTPAuthenticationError
3f5df62 feed: Add herror to _SOCKET_ERRORS and remove reason handing
c39625e error: Fix ProcessingError message and logging
a3719f8 feed: Catch parsing errors during html2text
a88738f error: Fix super calls for SMTPAuthenticationError, etc.
80a8edf email: Change stray SMTP_SERVER to server
a66dd58 email: Remove explicit ehlo() call
c9f5681 feed: Streamline rel-via title extraction in
  _process_entry_content()
aa8675d feed: Drop Google Reader rel-via manipulation
a226ef6 error: Fix inheritance typos for HTTPError (ProcessingError ->
  FeedError)

Signed-off-by: W. Trevor King <wking@tremily.us>