Fix: Migrate to react-codemirror2 (styleguidist#574)

Closes styleguidist#573

Fix: Fix parsing of error about webpack loaders

Looks like they’ve changed format and our RegExp doesn’t work anymore.
Anyway their error is now better, we just need to add a proper docs
link.

Closes styleguidist#575.

Fix: Update syntax in an example inside “Add examples to this component”

Fix: Lock jss-isolate version because of a regression in the latest p…

…atch release

cssinjs/jss#561

Fix: Pass devtool webpack option in dev mode (styleguidist#569)

Closes styleguidist#456

Fix: Support config theme overriding top level theme properties (styl…

…eguidist#566) (styleguidist#571)

Fix: Fallback to not formatting defaultProps (styleguidist#564)

Fix: Disable isolation for global CodeMirror styles

Fixes styleguidist#561

Fix: Read showCode option from the right place

styleguidist#561

Fix: Support to enable HMR for component dependencies (styleguidist#557)

Fixes styleguidist#551