Revert "disable new relic"

This reverts commit 48cf45c5f628d2d2b8ced1629684e18bae73b50b.
Update new relic
Revert "switch to unicorn"

The switch was done in order to see if puma may be related to 503
issues, but since it didn't change a thing, we may bring it back

This reverts commit 74612ed06789c5b000f44ba589aa07867a13a93a.