Update API documentation

I believe the documentation mistakenly references `mapDispatchToProps` when it means `mapStateToProps`. Users should pass `null` as the first argument (i.e. to `mapStateToProps` if they don't want to subscribe to store state), but still can get `dispatch` injected using `mapDispatchToProps`.  This commit fixes this reference.

Author: rmadsen

docs/api.md

@@ -58,7 +58,7 @@ It does not modify the component class passed to it; instead, it *returns* a new
 
   >The `mapStateToProps` function takes a single argument of the entire Redux store’s state and returns an object to be passed as props. It is often called a **selector**. Use [reselect](https://github.com/reactjs/reselect) to efficiently compose selectors and [compute derived data](http://redux.js.org/docs/recipes/ComputingDerivedData.html).
 
-* [`mapDispatchToProps(dispatch, [ownProps]): dispatchProps`] \(*Object* or *Function*): If an object is passed, each function inside it is assumed to be a Redux action creator. An object with the same function names, but with every action creator wrapped into a `dispatch` call so they may be invoked directly, will be merged into the component’s props. If a function is passed, it will be given `dispatch`. If you don't want to subscribe to store updates, pass `null` or `undefined` in place of `mapDispatchToProps`. It’s up to you to return an object that somehow uses `dispatch` to bind action creators in your own way. (Tip: you may use the [`bindActionCreators()`](http://reactjs.github.io/redux/docs/api/bindActionCreators.html) helper from Redux.) If you omit it, the default implementation just injects `dispatch` into your component’s props. If `ownProps` is specified as a second argument, its value will be the props passed to your component, and `mapDispatchToProps` will be re-invoked whenever the component receives new props.
+* [`mapDispatchToProps(dispatch, [ownProps]): dispatchProps`] \(*Object* or *Function*): If an object is passed, each function inside it is assumed to be a Redux action creator. An object with the same function names, but with every action creator wrapped into a `dispatch` call so they may be invoked directly, will be merged into the component’s props. If a function is passed, it will be given `dispatch`. If you don't want to subscribe to store updates, pass `null` or `undefined` in place of `mapStateToProps`. It’s up to you to return an object that somehow uses `dispatch` to bind action creators in your own way. (Tip: you may use the [`bindActionCreators()`](http://reactjs.github.io/redux/docs/api/bindActionCreators.html) helper from Redux.) If you omit it, the default implementation just injects `dispatch` into your component’s props. If `ownProps` is specified as a second argument, its value will be the props passed to your component, and `mapDispatchToProps` will be re-invoked whenever the component receives new props.
 
   >Note: in advanced scenarios where you need more control over the rendering performance, `mapDispatchToProps()` can also return a function. In this case, *that* function will be used as `mapDispatchToProps()` for a particular component instance. This allows you to do per-instance memoization. You can refer to [#279](https://github.com/reactjs/react-redux/pull/279) and the tests it adds for more details. Most apps never need this.