Implement a configuration wizard

[novemberborn]

It'd be great if we could ask (or auto-detect) the user whether they have Babel & TypeScript and set up AVA accordingly.

Similarly we could look at their project layout and suggest the creation of an initial test file (#14).

[novemberborn]

We could ask for the desired configuration format as well. Perhaps what kind of test suite they're writing in order to adjust the inactivity timeout.