www/rubygem-acts-as-taggable-on3: copy port

[xmj]

Summary

www/rubygem-acts-as-taggable-on3: copy port

With ActsAsTaggableOn, you can tag a single model on several contexts,
such as skills, interests, and awards. It also provides other
advanced functionality.

https://rubygems.org/gems/acts-as-taggable-on

(DiffRev: placeholder)
Approved by: swills (mentor)

Test Plan

http://xmj.me/freebsd/buildlogs/rubygem-acts-as-taggable-on3-3.3.0.log

[xmj]

use svn cp;
remove dependency on rails;
set dependency on activerecord4

[swills]

Approved!

[xmj]

Committed as 369406.