* remove length restriction on note
* add format validation for line_code

Without lambdas, Date.today will be evaluated in the class body.
For it to have a running scope of last week etc, it will need to
be evaluated each time the scope is called.
In Rails 4.0, lambdas will be required for all scopes, so not a bad
idea to go ahead and change them all now.

Didn't bother with files in db/, config/, or features/

Allows to alert only the commit author when a new note is added on a commit, useful when gitlabhq is used for code
reviews, allows less noise with mails...