Create README.md
Update Announce.php

Adding dismissed timestamp
Adding dismissed timestamp
Adding dismissed timestamp
Adding dismissed timestamp
Adding dismissed timestamp
Adding dismissed timestamp
Adding dismissed timestamp
a
Fix syntax error
Whitespace
Pull request #3: Added timestamp of dismissal

When a message is edited, its timestamp is altered to the current time.
When a message is dismissed by a user in a context, the time of
dismissal is also recorded.

Messages that are altered after dismissal by a user, reappear in the
list of visible messages for that user
Predefault 'Location' select when there is only one value
Plugin url now points to mantisbt-plugins org on Github

Also updated John's email address
Complete README file