Fix legacy plugin hash population in #configure()

We need to compare the identity of the plugin constructor with the
registered constructors, rather than checking whether the plugin
object is an instance of the class. The reason is that the latter
gives false positives when plugins inherit from other registered
plugins.
Make .attach() fluent, returning this
Stop using custom events in events hash

Part of #318
use new way of loading uris
Brace style test against minor browser difference

Might be 0pt or 0px or whatever.
do not add alternate languages as equivalent document

anchoring will fail in most cases for translated documents
Merge pull request #356 from scharf/issue_355

do not add alternate languages as equivalent document
Merge pull request #354 from scharf/issue_352

use new way of loading uris
Remove unused highlightRanges code
Set 'annotation-id' data attr on highlight elements

This allows the implementation of hover styles for specific annotations
across multiple highlight elements, as requested in #232.

Fixes #232.
Explicit argument passing in xpath.coffee

Let's remove some of the magic this usage here and make it clear
that things work on jquery objects.
Correct comments in xpath.coffee
Add tests and clean up document alternate ignores
Merge remote-tracking branch 'upstream/master'