timrogers / gh-migration-audit

* add auth strategies for supporting diff auth types * refactor to fix missing value * move createAuthConfig to bottom of file * rename file to be auth * add support to pass a string for token or an AuthConfig object * add test for token * add tests for auth file * add tests to check for case when values are set from env vars * add in additional options supported for auth * add samples to README for the new options * move tests to correct folder * remove unnecessary use of client id and client secret as well as auth type * update info message * add env var check for private key file and add test case for it * adjust order of options and add .env to indicate in --help the associated env var * remove need to have both private-key and private-key-file options, now only need private-key and check is done to see if is a *.pem file * update authentication section of README to be clear on the two approaches * remove check that the value starts with the RSA text