Document Testing Strategy

As a developer, I want to know the preferred testing strategy for OpenLMIS development, so I can focus and write tests appropriately.

We have some testing guidance in openlmis-template-service/readme.md, but it does not dictate the types of tests we expect developers to write, i.e. what is their responsibility.

Acceptance

1. Draft testing strategy and share with team. The strategy should indicate who is responsible for what, in priority order. E.g. mandatory for devs write unit tests for new and update code; mandatory devs write API/web tests for any RESTful interface changes;

2. Incorporate feedback, and publish. Remove extensive unit test guidance from openlmis-template-service/readme.md and move into this new document.