Add code infrastructure for supporting integration tests

[oubiwann]

Probably this will mostly just involve:

• Running a local instance of the CMR
• Tagging integration and/or system tests appropriately (there's lein support for this)
• Adding a place in the code for sample/testing payloads and expected response data (Create a home for sample/testing payloads and expected response data #14)
• Documenting these and how to get set up
• Documenting how to create an integration test