feat(promises): Adds monitoring for promises, removes Node 6 support

Re-submission of updates to wrap functions that return promises, and officially supporting Node 8.10 and newer.

Author: mrickard

serverless.yml

@@ -2,7 +2,7 @@ service: iopipe-lib-master-acceptance-test
 
 provider:
   name: aws
-  runtime: nodejs6.10
+  runtime: nodejs8.10
   stage: prod
   region: us-west-2
   role: ${env:IAM_ROLE}