function isRelativePath(path) {
            // If the path contains a colons it must be a full path on Windows (colons are
            // not valid path characters on mac or in URIs)
            if (path.indexOf(":") !== -1) {
                return false;
            }
            
            // For everyone else, absolute paths start with a "/"
            return path[0] !== "/";
        }
Creates or looks up a file.

@param {string} path Either an absolute path or a relative path from this
       DirectoryEntry to the file to be looked up or created. It is an error
       to attempt to create a file whose immediate parent does not yet
       exist.
@param {Object.<string, boolean>} options
@param {function (number)} successCallback
@param {function (number)} errorCallback