Add timeZone prop to IntlProvider

[jeremyyap]

Resolve #702

This adds a timeZone prop to IntlProvider which will be used as the default timeZone for formatDate and formatTime.

My team would like to see #707 merged but there has been no activity for two months. Here are the same commits with the requested changes.

[yahoocla]

Thank you for submitting this pull request, however I do not see a valid CLA on file for you. Before we can merge this request please visit https://yahoocla.herokuapp.com/ and agree to the terms. Thanks! 😄

[allenwq]

+1 For this !

[jeremyyap]

Hi @ericf! This PR is quite critical to ensure our app's progress - have you had any chance to take a look at it? 🙏

Thank you very much! Cheers!

[mv-stripe]

Bump :)

[potty]

+1

[okuryu]

Perhaps we should import PropTypes from prop-type in React 15.5?

[jeremyyap]

Thanks for reviewing! I've updated the example app to use React 15.5.

[MikkoIdean]

+1

[Calvein]

@ericf is there any update on merging this PR ?

[neutraali]

This would be super convenient to have ... Preferrably sooner rather than later. 😸

[okuryu]

Could you resolve the conflicts for this?

[jeremyyap]

@okuryu updated!

[samlecuyer]

@ericf or @okuryu any chance you'd merge this?

[couds]

+1. any update?

[papasmile]

+1

very minor q on package dependencies: are you able to uplift to latest react/react-scripts (16.2,1.0.17)?

[gameunite]

It's been a long time. Any update about this?

[eMarek]

Any plans to merge this?

[alexhoma]

Hi! all checks have passed, would anyone merge this PR? :)

[dteirney]

+1. Is there a timeframe for when this capability will become available?

[sourabh2k15]

Hi all, I have volunteered to maintain this project and this specific PR seems to be really important for a lot of folks. I am working on reviewing this PR, let's get this merged as soon as possible without further delay

@jeremyyap, thanks for all the work put in