Typo fix s/destroy/destroy()/

As requested by jpetitcolas at #249 (comment)

README.md

@@ -87,7 +87,7 @@ In addition to this configuration object, it also exposes some public members al
 *   **scale()** provides the horizontal scale, allowing you to retrieve bounding dates thanks to `.scale().domain()`,
 *   **filteredData()** returns an object with both `data` and `fullData` keys containing respectively bounds filtered data and full dataset.
 *   **draw(config, scale)** redraws chart using given configuration and `d3.scaleTime` scale
-*   **destroy** execute this function before to removing the chart from DOM. It prevents some memory leaks due to event listeners.
+*   **destroy()** execute this function before to removing the chart from DOM. It prevents some memory leaks due to event listeners.
 *   **currentBreakpointLabel** returns current breakpoint (for instance `small`) among a [list of breakpoints](./docs/configuration.md#breakpoints).
 
 Hence, if you want to display number of displayed data and time bounds as in the [demo](https://marmelab.com/EventDrops/), you can use the following code: