Test cases for testing ErrorMessageFactory. Fixes T864

Summary:
 - Add tests for ErrorMessageFactory class
 - Use Gradle port of espresso

Test Plan:
 - Run `./gradlew test`
 - Then `./gradlew connectedAndroidTest`
 - See tests pass

Known issue. For reason it fails at the end with a message `No tests found.`
which isn't related to any of the tests. Will look into this later

Reviewers: dkobia, PapaLee

Subscribers: rjmackay, shadowhand

Maniphest Tasks: T864

Differential Revision: https://phabricator.ushahidi.com/D414