0.10.8: New `$imports` feature

• New $imports feature allows declaratively importing wire specs. Check out the docs for more info.
• Minor internal unit/integration test fixes:
  • Workaround gent+buster integration issue and update to gent 0.6.x. This only affects the ability to run unit tests.
  • Fix unhandled rejection in unit test--exposed by when.js 3.2.x's new unhandled rejection reporting, win.