7.x grammar fixes
Merge pull request #12 from daitken/7.x

7.x grammar fixes
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...