Fixed the problem where a user resaving a current open diary day would
create a new entry in the DB. This still has to be fixed for the
entrytag junction table.
Changed the name of writeData to writeDay to match the naming of the
opposite function readDay.
Added simple (naive) fix to take care of the fact that entrytag's would
get duplicated in the DB when resaving the same existing day. Doesn't
seem like the most sophisticated way to do this but it works.
Added function to the Diary to clean the tags when saving. This takes
care of the case where a user deletes a tag from the text when resaving
the day. Previously this tag would continue to exist in the DB forever
even if it didn't exist in any entry.