Implement sentry to get runtime exceptions and other errors

[parberge]

Why:

Today when an error occurs we need to login to AWS and look through cloudwatch logs to debug the error.
We should leverage sentry to pickup these errors and notify us in slack.

Actions:

• Setup sentry in the code
• Setup sentry to send us notification

this issue is a follow-up of #18

[parberge]

This seems like a perfect lib for us to use:
https://pypi.org/project/sentry-chalice/