Improve deployment experience

[itowlson]

This PR:

• modifies the sloth warnings to be "checking status" (for the Hippo health check) and "uploading application" (for Bindle) instead of warning about a slow response
• adds the "wait for application ready" UI when deploying using a GH token, so the user is less likely to see the 404 of application not ready

It also removes what seems to have been a duplicate sloth warning for the bindle upload, probably a spurious leftover from an earlier merge.

[mikkelhegn]

This experience is much better now - Thx @itowlson!