Unify using chai.expect

- [ ] `unit`
  - [x] blueprints
  - [x] broccoli
  - [x] cli
  - [ ] commands
  - [ ] errors
  - [ ] models
  - [ ] package
  - [ ] preprocessors
  - [ ] settings-file
  - [ ] tasks
  - [ ] ui
  - [ ] utilities
  - [ ] analytics-test.js