Remove text-shadow mixin calls

After further research, this mixin doesn't add any value http://compass-style.org/reference/compass/css3/text-shadow/
- Removed the call in footer-ie since the property is only supported
IE10+
- Standardize all calls to use the colour last format

Since the property is only supported in IE9, a custom mixin may be
desired to polyfill with the MS filter version