function getFileExtension(fullPath) {
        var baseName = getBaseName(fullPath),
            idx      = baseName.lastIndexOf(".");

        if (idx === -1) {
            return "";
        }

        return baseName.substr(idx + 1);
    }
Get the file extension (excluding ".") given a path OR a bare filename.
Returns "" for names with no extension. If the name starts with ".", the
full remaining text is considered the extension.

@param {string} fullPath full path to a file or directory
@return {string} Returns the extension of a filename or empty string if
the argument is a directory or a filename with no extension