Update: WordPress 3.6 compatibility
Optimize: Responsive lightbox display on mobile devices
Theme: Remove viewport modifications

* High potential for unexpected behavior.
* SLB theme will be responsive on responsive WP themes
Theme: Increase overlay min-height

Accommodate extra space on mobile browsers when URL bar slides out of view on vertical scroll
Viewer: Adhere to user-set `loop` option

Lightbox closes on first/last group item on prev/next navigation respectively if looping is disabled.
Viewer: Validate theme before showing item

Viewers with invalid themes will stop processing immediately and allow browser to handle event
Themes: Organize assets

* Move: Stylesheets to appropriate subdirectories
* Add: Compass config file
* Update: Paths to theme assets for theme registration
Themes: Update asset paths

* Images
Legacy IE Compat: Screen width and Image Dimensions

Image Handler
* Update: Use jQuery event binding
* Update: Reference image object directly (IE8 sets `this` as `window` object, not object that triggered event)

Theme
* Fix: Switch from `window.outerWidth` to `document.documentElement.clientWidth` for measuring viewport (`window.outerWidth` not supported in IE8)
* Update: Refactor styles to use Compass mixins
* Optimize: Use opacity mixin (for IE8 compatibility)
Theme: Optimize media query targeting for small-screen devices
Legacy IE Compat: Remove `Array.indexOf()` references

IE8 does not support `Array.indexOf()`

* Update: Use `jQuery.inArray()` instead
* Remove: `Utilities.arr_indexOf()` (Redundant)
Update readme: 2.0RC4 Release notes
Prep for release: 2.0RC4

* Remove: debug code
* Update: version
* Update: Plugin URI
Merge branch 'release-2.0RC4'