Skip Style Checks on Invalid apps

[bcooksey]

Description

If a dev has an app that has major schema validation errors (but still parses as JSON), the zapier validate command will POST that to zapier.com to run the style checks. In some cases, this can cause the server to throw a 500. That is being fixed, and will soon correctly return a 403.

However, there really isn't a point in making that call at all if we know locally we are invalid. So, this PR updates the validate command to skip style checks on invalid apps.

TODO

• Skip style check API call on invalid app
• Do not print success message if style checks are skipped due to invalid app
• Do not print success if -without-styles flag is passed.

[bcooksey]

I should mention that the process.exitCode may not be the cleanest solution now that we are skipping stuff. As an alternative we could use process.exit(), though it is nice to flow through the whole chain so that each callback can be responsible for saying messages like "Skipping because", vs the point calling process.exit() having to be aware of what all other things are skipped. Maybe a throw and .catch could solve that.

[BrunoBernardino]

I see what you're saying. I think this works well for now. If we find we need to add a bit more structure and control we can always improve that later.

This makes sense and is a nice, clean solution! Thanks!