Add a directive to track "since" version information

[aprescott]

It can be useful when reading documentation to know in which version a method was first available. For example, when looking at Ruby's Enumerable#max_by latest documentation and wanting to know when it was first available.

A :since: <version> directive would support this.

[drbrain]

I approve this idea.

I think the directive should be only a version.

This would allow RDoc to have a page listing all the methods and their date of introduction.

Any details about changes to the method across versions should be listed in prose.

Also, Since: <version> should be acceptable since it looks more like plain text.

[zzak]

fwiw, apidock does something like this already: http://apidock.com/ruby/Enumerable/max_by
http://apidock.com/faq#What-is-the-bar-graph-on-the-top-of-documentation-pages

[drbrain]

Not enough time for this in RDoc 4.1, moving to the next release.

[zzak]

You can see the rurema syntax here and here

[zzak]

More info from the rurema wiki