Modal Component

[jefferscn]

This patch solves the following problem
#91 Modal Component

• use react-transition-group to implement animation.
• for some problem when modal renders in a fixed element in browser(specially Safari),We render the modal root element out of the main app tree.Create a new div under body,then render all modal conent into this div.
• document is copied from Add Modal component #411

Test plan

• default value test
• root element test

This pull request

• includes documentation
• includes tests
• includes benchmark reports
• includes an interactive example
• includes screenshots/videos

[vaukalak]

Does anyone know what is the status of this PR, and if the help is needed on that?

[piranna]

Can somebody fix the conflicts an merge it upstream?

[piranna]

By clossing this, does it means it's upstream already and published on npm?