v3! "Closest" feature, prometheus support and much more

April 2019

• Added Prometheus metrics support
• Removed /monitor websocket interface
• Removed /status and /status.json pages
• Support "closest" matching (instead of geo/asn labels) for A and AAAA records (Alex Bligh)
• Support for GeoIP2 databases (including IPv6 data and ASN databases)
• "Pluggable" targeting data support
• Support for "health status" in an external file (not documented)
• Integrated health check support coming later (integrated work done by Alex Bligh, but not functional in this release - his branch on Github has/had it working)
• Remove minimum TTL for NS records (Alex Bligh)
• More/updated tests
• Don't let the server ID be 127.0.0.1
• Use 'dep' to manage dependencies
• Remove built-in InfluxDB support from the log processing tool