Added Design Decisions and Audit Guide Documents

[JonathanChristopherson]

This PR adds the following new files:

• docs/designDecisions.md - A place for us and future developers to better understand some of the decisions which were intentionally weighed and discussed in developing the application. This gives an opportunity for consistency in delivery and allows us to refactor or "re-decide" at a future date when conditions change. This PR should resolve Issue #31
• docs/auditguide.ipynb - A document to serve two purposes (further described in the document itself), to provide guidance to an auditor evaluating what these metrics evidence, and to provide a simple, sample visualization of the metrics. This PR provides an initial template to move toward resolving Issue #24 , but does not fully resolve it yet.

This PR adds a minor update to the following file:

• .gitignore - Added in the .DS_STORE file which comes along with some filesystem conversions. Let's avoid hitchhikers.

Further Decisions: We will want to decide what kernel to use for the Audit Guide, whether to use the default Python kernel, a Go kernel (in better alignment with the rest of the code), or something else. Once we decide on the kernel, the rest of the document content can be pursued.

[JonathanChristopherson]

No Tests have been developed yet, so no tests passed, nor did any fail.