Make some changes around width and height params

* width comes before height
* don't resize an image if no dimensions are specified
* factor out logic to extract dimensions from request
Refactor GiltRetriever

* factor out generic URL downloading into UrlRetriever
* add a bit of logging
Changes to Resizer

* remove ScrimageResizer (and deps) - couldn't get it to render
without overlying reddish hue
* implement AwtResizer which directly uses the Java APIs