Add basic linter to project

[alexandrebarbaruiva]

New Feature Submissions:

To run tests locally, use make if you're on Mac or Linux.

1. [X] Does your submission pass all the tests?
2. [X] Have you lint your code locally prior to submission?
3. [X] Have you written proper tests to your added code?

New Dialog Submissions:

User messages have - -, bot messages have -

1. [ ] Does all your user messages have lower letters?
2. [ ] Have you lint your dialogs locally prior to submission?
3. [ ] Have you written proper tests to your added dialogs on test_dialogs?
4. [ ] Does your dialog have an existing category? If not, did you create it?

Changes to Core Features:

• [ ] Have you added an explanation of what your changes do and why you'd like us to include them?
• [ ] Have you written new tests or modified old ones for your core changes, as applicable?
• [ ] Have you successfully ran tests with your changes locally?