Handle loading state

[Connoropolous]

When it's loading a flow design it says 'loading' but can get stuck

[Bortseb]

from terminal while error happened:

(node:26452) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: Connection to ws://noflo-rsf.herokuapp.com timed out
(node:26452) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.