Test enhancements to Navigator status.

* Used minitest spec reporter for more color.
* Added diff ANSI color output to test console.
* Reduced backtrace too noise so diff ANSI output is clean looking.
* Diff output is saved to an `output` directory. This folder is checked in, but files are ignored.
* Test files are discovered automatically.
* Test files can be recursive in directories. Output of DIFF matches new dirs too.