In-app message to show connection errors in DEV

Client side, it'd be great to allow people to add some kind of `` component which could popup if reactotron can't connect and we're in dev mode.

#63

The problem with using a `console.log` is that people might not see it if they've got yellow box off.

The issue names no files or tests; start by reviewing issue #63 and locating the client-side connection handling for React and React Native. Define the development-mode ReactotronStatus behavior and its connection-error popup, with completion shown by coverage for failed connections rather than relying on console.log.

Written by the indexing model from the issue text.