Global exception handling

[leonardowf]

It would be nice if the application did not crash completely when we invoke an endpoint with an invalid project key.

Edit: The issue is caused by eager x lazy conversion of promise to rxjs

Reference: https://stackoverflow.com/questions/39319279/convert-promise-to-observable/69360357#69360357

Reference: https://blog.heroku.com/best-practices-nodejs-errors

[leonardowf]

Closed by #132 and #133