Fix path matching issue with usemin on Windows

When you are working with both Windows and Linux, a common solution must be used for how path are compared with usemin:

	ngtemplates: {
		dist: {
			options: {
				usemin: 'scripts' + Path.sep + 'scripts.js',
			}
		}
	}

It would be better instead to normalize the path specified in the build:js section and compare with the file system result.

Note that tests were not updated because they will not run on Windows (I attempted to fix them quickly but I don't have more time to put on this at the moment)