Allow notification of when a tracked post is edited

[flamencanyc]

Title
Allow notification of when a tracked post is edited

Short, concise description of the idea
Add an option to the "notify me when" choices to allow the user to be notified when a tracked post is edited.

Full description of the idea
See above.
An ordered list of benefits

• Allows a user to know when a post of interest is edited/modified.
• Keeps interested readers from missing important info that is added to a post after the fact.
• Especially useful when a single post is used to keep a running list of something that is updated multiple times in the future.

An ordered list of problems/issues involved

• Can't think of any, unless there is difficulty in doing this technically.

An organized list, or a few short paragraphs detailing suggestions for implementation

• The tech side is up to you guys if you like the idea.