start = function () {
            if (options && options.notebook_path) {
                that.notebook_model.path = options.notebook_path;
            }
            if (options && options.kernel_name) {
                that.kernel_model.name = options.kernel_name;
            }
            that.kernel_model.id = null;
            that.start(success, error);
        }
Restart the session by deleting it and the starting it
fresh. If options are given, they can include any of the
following:

- notebook_path - the path to the notebook
- kernel_name - the name (type) of the kernel

@function restart
@param {Object} [options] - options for the new kernel
@param {function} [success] - function executed on ajax success
@param {function} [error] - functon executed on ajax error