Update generator to yeoman-generator 0.17

TODOs:

- [ ] Tests failures due to https://github.com/yeoman/generator/issues/614
- [x] Need to update (more) to using File-utils and not the legacy methods
- [x] Need to update to the new tests utilities (both template and test code - test code is pretty raw, it'd be great to test more thoroughly)
- [x] Run tests in a tmpdir rather than in `./tmp`
- [x] generate `.yo-rc.json` file (require tmpdir fix)
Haven't had the time to test run this, but what happens if the name is taken and the users anwers yes on the prompt to choose another one? Is the previous question prompted again?