Starting to improve documentation

Updating with spawning specifier behavior, and adding mark and stitch libraries.

Updating Tracey core libraries, including a new drag analysis library and parsers for span and trace position specifiers and for transformation templates.

adding teaser to readme.md

updating go module to support all packages

trying to get package setup

Updating critical_path, smart_dependencies, test_trace, and transform packages. Adding antagonism package.

Updating package trace

Updating package trace

Adding CONTRIBUTING.md

Adding license

Initial checkin of trace libraries

Adding README