Resources with same basenames (different extensions) are excluded from build

[alectolytic]

Came across this issue while trying to include the foundation-icons [1].

This can be reproduced by adding two files of same name but different extension to resources/base. Eg: filename.css, filename.png

This happens even if the files are in different sub-folders, I suspect the issue is at core/resources.js file.

[1] http://www.zurb.com/playground/foundation-icons