Don't use XRegExp for Ovid Tagged

As far as I can tell was the only use of XRegExp outside of an export
translator. This means that we won't need to load XRegExp for anything
but export.

I'd eventually like to kill XRegExp entirely because:

- It's extra code that is not used in many places.
- Sandboxing it is disproportionately painful because it creates new
  object instances. (Every web translator now works in Firefox 33, but
  I'm not sure if XRegExp is entirely broken or it was just line 229
  here.)
- ES6 Unicode regexp support should eventually make it unnecessary.
Merge pull request #786 from zotero/sjk/ovid

Don't use XRegExp for Ovid Tagged
[Amazon] Fix multiples
Re https://forums.zotero.org/discussion/41334/more-than-4-items-on-folder-list-from-amazon/
[YouTube] Don't mix HTTP/HTTPS protocols
[YouTube] Fix multiples
[Amazon] More multiples variations
Same page served in different formats for different sessions... (same browser!)
[ACS Publications] Fix multiple detection
* Clean up outdated target URLs
* Recognize ToC pages that were already in the tests, but failing with regexp (see zotero/zotero#558
* Add support for "Subject Search" (/topic/), and search result pages
handle time.com, and scrolling article page
[Time.com] Pass through JSBeautifier, minor cleanup, fix detectWeb
All tests pass with same data as before.
Closes #788
CC @aepheus
[Cambridge Journals] Fix PDF downloading. Expand multiple detection
Add new translator for Bundesgesetzblatt (Federal Law Gazette of Germany)
Merge pull request #790 from zuphilip/master

Add new translator for Bundesgesetzblatt (Federal Law Gazette of Germany...