* WIP: Implement HTTPS interception detection by Durumeric, et. al.
Special thanks to @FiloSottile for guidance with the custom listener.
* Add {{.IsMITM}} context action and {mitm} placeholder
* Improve MITM detection heuristics for Firefox and Edge
* Add tests for MITM detection heuristics
* Improve Safari heuristics for interception detection
* Read ClientHello during first Read() instead of during Accept()
As far as I can tell, reading the ClientHello during Accept() prevents
new connections from being accepted during the read. Since Read() should
be called in its own goroutine, this keeps Accept() non-blocking.
* Clean up MITM detection handler; make possible to close connection
* Use standard lib cipher suite values when possible
* Improve Edge heuristics and test cases
* Refactor MITM checking logic; add some debug statements for now
* Fix bug in MITM heuristic tests and actual heuristic code
* Fix gofmt
* Remove debug statements; preparing for merge
