getReadAsMethod: return method name for 'readAs*' - http://www.w3.org/TR/FileAPI/#reading-a-file
function getReadAsMethod(type, readAsMap, readAsDefault) {
        for (var r in readAsMap) {
            if (type.match(new RegExp(r))) {
                return 'readAs' + readAsMap[r];
            }
        }
        return 'readAs' + readAsDefault;
    }