Add a couple functions to extract the version number.
Provide alternate image paths for older OpenSeadragon.

Addresses OnTime ticket 904. Also, update the README with a working
download link.
Use file_create_url() to avoid concatting manually.
Merge pull request #13 from adam-vessey/7.x

Address some version compatibility issues with the OpenSeadragon library.
Simplify version checks...

...  Probably should have poked around first.
Merge pull request #14 from adam-vessey/7.x

Simplify version checks...
Check the zoom levels to determine what dimensions the clip will be.
Rework based upon feedback.
Merge pull request #15 from jordandukart/7.x

Check the zoom levels to determine what dimensions the clip will be.