Go-Looking Glass v1.2.0

N.B. this release contains a slight breaking change; the server sub-command has been renamed to serve.

Changes since last release:

• Bump dependencies.
• Add X-Powered-By header.
• Improve support for reverse proxies.
• Implement various logging improvements.
• Handle SIGINT, SIGQUIT and SIGTERM signals.
• Use a thirty second shutdown timeout.
• Rename web server command.

Full Changelog: v1.1.0...v1.2.0