Fixed #69

[pierreericgarcia]

next is actually the second parameter of the onPress callback function !

As pointed out in the issue 69, when we try to use the next function in the onPress callback we get an error : next is not a function. Because the first argument of the onPress callback function is actually a ref !

As we can at the line 160 of the file components/AwesomeButtonProgress/index.js :

action(this.content, this.endLoading.bind(this));

The next function is actually the second argument ! As it would be a breaking change to swap the argument order I propose to update the documentation which is misleading.