Test cases for presenters. Fixes T866

Summary:
 - Test cases for `AddDeploymentPresenter` class
 - Test cases for `UpdateDeploymentPresenter` class
 - Test cases for `DeleteDeploymentPresenter` class
 - Test cases for `DeploymentListPresenter` class
 - Upgrade roboelectric gradle plugin
 - Update readme file. Providing the right commands to run tests

Test Plan:
At the root of the project
 - Run `./gradlew :app:connectedAndroidTest`

Reviewers: PapaLee, dkobia

Subscribers: shadowhand

Maniphest Tasks: T866

Differential Revision: https://phabricator.ushahidi.com/D416