Send email claim welcome pack

[gndelia]

Closes #45

This PR

• Adds the call to the webhook to send an email when the user claims a token. I had to reorganize the code so the timestamp would be sent and saved in our database as well
• Added tests
• Run these tests on GH
• Added a fake lambda to use in local env as "sending emails" instead of using a webhook. I left it commented so it doesn't leak to prod (I'd rather have it fail locally rather than deploying this to aws). I tried this serverless plugin but it does not seem to work with serverless-offline (I left them an issue Does this work with serverless-offline? abemedia/serverless-disable-functions#259).
• Added permissions to migrations-pg once it runs in aws