add offsetTop of each of the element's offsetParents
`while(--i)` -> `applyEach` for `changeDivsToEmptyImages`
`while(--i)` -> `applyEach` for `checkImagesNeedReplacing`
Adding dedicated fixtures for responsive images
Using only fixture images, no network call.
Merge pull request #60 from marcinwenger/element-offset-top

add offsetTop of each of the element's offsetParents
Merge branch 'fix-loop-order' of https://github.com/oncletom/Imager.js into oncletom-fix-loop-order
Merge branch 'fix-404' of https://github.com/oncletom/Imager.js into oncletom-fix-404
`window.addEventListener` -> `var addEvent`
Sauce Remote Testing
Using bundled Travis Sauce addon
Changing tests to see if chai can be possibly compatible with IE8