Update Gemfile.lock to point to an available version of newrelic gem

* Did another bundle update to pull in the latest version of newrelic
* It appears newrelic published a version of their gem then removed it
* The version in the lock file was 3.5.6.46
* There is only a beta version of this number available on https://rubygems.org/api/v1/versions/newrelic_rpm.json
* The latest version of the gem is 3.5.6.55
* When tddium attempted to bundle the gem was not found