Dependency upgrades and tooling tweaks

Keeping dependencies up to date:

• Upgrade jest from 23.6.0 to 24.1.0
• Upgrade eslint-config-prettier from 3.3.0 to 4.0.0
• Upgrade eslint-plugin-import from 2.14.0 to 2.16.0
• Upgrade prettier from 1.15.3 to 1.16.4
• Upgrade eslint-plugin-jest from 22.1.2 to 22.2.2
• Upgrade botkit from 0.6.21 to 0.7.2
• Upgrade eslint-plugin-prettier from 3.0.0 to 3.0.1
• Upgrade eslint from 5.10.0 to 5.13.0

Linting and testing tooling is now dogfooded within this repository.