rename overscan props for Gird with deprecation

[nihgwu]

close #226

[bvaughn]

This looks solid. One small request to split up the deprecation message if you're willing.

[bvaughn]

I think this message may be a bit confusing for people who were unaware of the old overscanCount prop. Seems like it would be better to split these into two warnings?

[nihgwu]

OK, will do

[nihgwu]

Hey @bvaughn , I'd like to ask for your help for an off-topic problem, Autodesk/react-base-table#22, do you have any idea to avoid a second rendering to solve the problem, that is if I know it's a pure client rendering I could just use the real scrollbar size in construction, or I have to update it in cDM

I also found that in react-virtualized https://github.com/bvaughn/react-virtualized/blob/master/source/Grid/Grid.js#L610 this statement is wrong, and it won't work actually, as in client hydration the component's constructor render will be called again and the scrollbar size is measured there, so this block won't be hit at all

I noticed this problem after I migrated to react-window, it wasn't a problem as I always do a second rendering because I relied on onScrollbarPresenceChange from Grid before, but now I calculate it by myself for migrating to react-window

[bvaughn]

Thanks!

[bvaughn]

I think you forgot to rename overscanRowsCount -> overscanRowCount for the pre-existing one. 😁 I'll do it!

[bvaughn]

Released in 1.8.2 - https://github.com/bvaughn/react-window/blob/master/CHANGELOG.md#182