package:api_summary v1.1.0

• Added expectApiSummaryClean, ApiSummaryFormat, and
  ApiSummaryVerificationException to support one-liner golden file verification
  in dart test (e.g. test('api_summary', expectApiSummaryClean);).
• Added --write (-w), --check (-c), and --output (-o) flags to the
  api_summary CLI executable.