Update README.md

Updating the with basic info and instructions.
Improving description.
converting shunit2 tests to bats tests, updaing travis-ci scripts to use bats
making script executable in CI setup
adding local path to PATH
fixing unittest which needed to be wrapped in quotes
adding test where variable is set in test
testing if not using variable fixed issue
commenting out expected usage tests that run locally but fail on travis
adding .sh suffix for clarity, updating tests