#388 Proposed loader enhancements (most is in)

See new example weatherWithLoad for demo. Depending on APIs, "Loading image" or "Getting forecast" will display longer. Use $timeout around loader.stop to try out options.

Refer to issue #388 for features added

Not in: reset (on route change and on scope destroy)

Changed from #388: Keep the options object and use it for content and timeout.
DOM related options set in the directive.