Add run subcommand (#529)

* test: fix TestGetConfigFilePath

This test wasn't correctly creating the test file due to the wrong directory permissions on the temp file. This wasn't detected due to a lack of error checking.

Also, the code was only checking for file not exist rather than lack of permission to read file (or any other error).

The combination of these two things means the test wasn't checking what it thought it was checking, and passed more by luck than judgment.

* add getYamlFilesFromDir

* add getTestYamlFiles and test

* docs: Update master / node help text

* return path + filename from getYamlFilesFromDir

* subcommand run to run specific section files