adding warning about the lack of support for onScroll on IE8

Adding `console.warn` about the lack of support for `onScroll` event on IE8
Related to this issue on github https://github.com/facebook/react/issues/631
Add jsx-requirejs-plugin to the tooling-integration page
Remove the require-jsx plugin from the tooling-integration page

In favor of the r.js friendly jsx-requirejs-plugin
Mention react-art where we talk about SVG
Fix typo
Add gulp-react to Helpful OSS Projects

Add @sindresorhus' JSX task for Gulp to the "Helpful Open-Source Projects" section of the tooling integration docs.
Document displayName
Add link to HTML to JSX converter to “JSX In Depth” page
Change “not allowed” back to “discouraged” since you technically *can* use props called `class` or `for`…
Community Round-up #14