Unit tests for Gnip connection handling

- Gnip interface is injected into CognicityReportsPowertrack object for
testability
- Updated JSDoc
- Added unit tests for connectStream function testing; exponential
backoff reconnection delay, maximum reconnection delay parameter,
disconnection warning only sent once per failure, disconnection warning
sent again if reconnected and disconnected
Unit tests for Gnip connection handling

- Gnip interface is injected into CognicityReportsPowertrack object for
testability
- Updated JSDoc
- Added unit tests for connectStream function testing; exponential
backoff reconnection delay, maximum reconnection delay parameter,
disconnection warning only sent once per failure, disconnection warning
sent again if reconnected and disconnected
Test for app.js startup

- Test that we can run app.js with the default config and that it fails
with an exit code and doesn't throw an error