Framework: Update npm packages to remove warnings from the console

[gziolo]

Description

Fixes #3107. This PR updates a few npm packages to get rid of npm warnings:

npm WARN babel-loader@6.4.1 requires a peer of webpack@1 || 2 || ^2.1.0-beta || ^2.2.0-rc but none is installed. You must install peer dependencies yourself.
npm WARN react-autosize-textarea@0.4.8 requires a peer of react@^0.14.0 || ^15.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN react-autosize-textarea@0.4.8 requires a peer of react-dom@^0.14.0 || ^15.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN react-datepicker@0.46.0 requires a peer of react@^0.14.0 || ^15.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN react-datepicker@0.46.0 requires a peer of react-dom@^0.14.0 || ^15.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN react-slot-fill@1.0.1 requires a peer of react@^15.5.8 but none is installed. You must install peer dependencies yourself.
npm WARN react-transition-group@1.2.0 requires a peer of react@^15.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN react-transition-group@1.2.0 requires a peer of react-dom@^15.0.0 but none is installed. You must install peer dependencies yourself.

There is still one warning logged on the console:

npm WARN ajv-keywords@2.1.0 requires a peer of ajv@>=5.0.0 but none is installed. You must install peer dependencies yourself.

It comes from the enzyme package which I updated to the latest version. I would wait until it's resolved on the enzyme side.

It also fixes new lint option for Jest:

30:27 warning Use toHaveLength() instead jest/prefer-to-have-length

How Has This Been Tested?

npm test & npm dev still work.

Tested manually in the browser.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows has proper inline documentation.

[gziolo]

Eslint had some issues with having this inlined ...

45:5 error Your render method should have return statement react/require-render-return

[gziolo]

It looks like it is no longer used. I removed it.

[mtias]

Are we still using this?

[gziolo]

Yes, we display badge in Readme based on it.