Fix: Support new flow 0.53 annotations (styleguidist#602)

Update React Docgen for support of the new Flow 0.53 annotations:
reactjs/react-docgen#209

Fix: Add depth to sections so heading levels are correct (styleguidis…

…t#601)

Closes styleguidist#600

Fix: Improve terminal output on style guide server start (styleguidis…

…t#595)

Closes styleguidist#470

Fix: Create custom JSS instance

To prevent manipulations on the default instance (like plugins setup)
affecting Styleguidist styles.

Fix: Omit component if propsParser returns an empty array (styleguidi…

…st#588)

Fix: Prefix generated by JSS class names

To prevent collisions when user app also uses JSS.

Fix: Inherit font-size to make em sizing work properly in components (s…

…tyleguidist#585)

Close styleguidist#584

Fix: Do not lowercase nested keys of example settings object, pass pr…

…ops to Preview component

Fix: Pass example file path to updateExample (styleguidist#583)

Close styleguidist#579.

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

Closes styleguidist#573