Do not mix production and development version of create-react-class

[amanmahajan7]

Description

Fix false positive getDefaultProps warnings. Fixed #978

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/adazzle/react-data-grid/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here)
React 15.5 deprecated React.createClass and added a warning when getDefaultProps() method is used with class components (React.component). These deprecation warnings are only shown in development mode. Components created using React.createClass or createReactClass still use getDefaultProps() method to define defaultProps. In development mode, React sets a flag isReactClassApproved to suppress these warnings for components created using React.createClass or createReactClass.
react-data-grid.js bundles the min version of create-react-class (created using webpack) and because of this isReactClassApproved flag is not set anymore on the components created using using React.createClass or createReactClass.

What is the new behavior?
react-data-grid.js bundles the dev version of create-react-class
react-data-grid.min.js bundles the min version of create-react-class

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes
[x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:
This is a temporary fix, in the future when mixins are removed, remaining components can be converted to class components and create-react-class package can be dropped

[coveralls]

Changes Unknown when pulling e350009 on am-fix-defaultprops-warnings into ** on master**.

[jpdriver]

@amanmahajan7 what impact does this have on bundle size? 😳

[amanmahajan7]

@jpdriver, it does not change the bundle size by much, previously create-react-class was included by webpack, this PR includes it explicitly so we can control which version gets packaged.

Before

After

[audiolion]

+1 for this, getting all the warnings is pretty annoying

[stevewillard]

Any reason why this can't be merged?