Moved custom scroll parent to a prop called getScrollParent

[k2snowman69]

Resolves #177

Basic issue is based on documentation you should not inherit from react components, instead you should override using composition.

[danbovey]

Looking at adding this feature in the v2 branch as this will be a breaking change.

I've implemented a clearer getParentElement method that can be overridden with a customParent prop.

https://github.com/CassetteRocks/react-infinite-scroller/blob/3a707215dfd2065845d0d876c853a0253d866a03/src/InfiniteScroll.js#L30-L37

[k2snowman69]

With the way this is written currently, it's an entirely backwards compatible change. The majority of the change resides in getParentElement, the changes in attachScrollListener were mainly to reduce the number of calls to getParentElement for debugging purposes.

Digging into the backcompat scenarios:

1. If a user doesn't pass this.props.getScrollParent scrollParent is null and will result in the original el && el.element code being executed.
2. If a user does pass this.props.getScrollParent scrollParent then the resulting value is returned
3. If a user inherits from this component, they would override getParentElement and none of the code within this component would be executed. If they do call super, we end in the first scenario

As far as the naming, customParent sounds like you're wrapping the InfiniteScroll component with another custom element... it's a bit confusing to me without reading the documentation.

If you are still planning on only pulling this request into the v2 branch even though it's backwards compatible, let me know, I'll have to figure something out for the short term.

[danbovey]

You're right! That's great. I'll merge this now.

I'll use the getScrollParent prop in v2 as well, as it's is more intuitive that it expects a function returning an element.

[danbovey]

Released in 1.2.2. Thanks a lot!

[k2snowman69]

Thanks for the quick turn around!