Add Attributes formAction, formEncType, formMethod and formTarget

This resolves #2425.
Permit th  attribute
Update variable name and doc type to be accurate

Test Plan: Crossed fingers.
Finish renaming renderComponent -> render

Test Plan: jest
Merge pull request #2581 from spicyj/rm-elt-docs

Update variable name and doc type to be accurate
Merge pull request #2582 from spicyj/rendercomponent

Finish renaming renderComponent -> render
Add example for how to use `style` properly

Test Plan: jest
Merge pull request #2583 from spicyj/style-example

Add example for how to use `style` properly
react.js conf updates
better wording thanks to @jwalke
Mention that talks will be recorded
Use warning module for context warning instead of invoking console.warn and monitorCodeUse directly.  Depends on https://phabricator.fb.com/D1695279
Merge pull request #2579 from jsfb/context-to-warning-module

Use warning module for context warning instead of invoking console.warn ...
Add additional field for ART reconciler

ART, just like MultiChild adds an expando property to manage it's diffing
state. This is ugly and bad. We should be moving this state outside the
component for use by the diffing algorithm. This state is not needed by
components nested in composites, and varies by diffing algorithm.

It sucks that I have to add it to every component just to support ART,
but that's the quickest solution, other than disabling preventExtensions.

At least now we know that it sucks.
Merge pull request #2593 from sebmarkbage/mountImage

Add additional field for ART reconciler
Wrote Community Roundup #24
Community #24: New Carousel link, spelled react-prism correctly, and removed the whale-speak.
reactComponentExpect expects itself

This was a bug when reactComponentExpectInternal was separated from
the normal reactComponentExpect flow.
Merge pull request #2594 from steveluscher/community-round-up-24

Wrote Community Roundup #24
Replaced document.createElement with ReactTestUtils.renderIntoDocument where container was not subsequently utilized.
Fixes #1250