Multiple exported component definitions in one file

[embbnux]

Found that ConversationMessageList and Header component export multiple component in on file.
And it causes problems in docs gen.
React-docgen doesn't support to parse Multiple exported component definitions in one file.
We need to avoid to export multiple components in on file. It is not a standard way.

And found that we export some sub components in ConversationMessageList and Header file just for test.
Is it possible to test those component without exporting sub components in those file. @tylerlong