Ensure the we are only modifying the path name when adding @2x.

If `document.createElement()` exists use that to create an 'a' element to
parse the URL otherwise simply assume the first '?' seperates the query
params from the rest of the URL (weak assumption).

Reguardless of method used, run regex replace on the path part only to
prevent @2x from being added to query params.

See added unit test for more info.
Simplify REGEX

No need to look for '?'.
Allow some images to not be processed by Retina

We had a very difficult to track down bug wherein Retina was setting the width and height of an image to 0px after an ng-show trigger. This should not be happening, and one easy fix is to allow individual images to not be processed by Retina.
possible to exclude image with 'data-no-retina'
exclude images with data-no-retina

Images were'nt loaded in 'retinaImages'
Added data-no-retina
Added scss and sass partials
Added SASS documentation
Add tests for scss mixin
Fix interpolation in scss partial to render properly with libsass
Add config option for adopting the original image's dimensions
Remove extraneous quotes to url interpolation in scss partial
Version bump
resolve conflicts
Version bump to 1.2.5