Restore tests

[jmartin-sul]

• move back to version of swagger codegen that produces working client for us, restore integration tests to show it.
  • try swagger codegen 2.4.8, bump open api spec version to 3.0.2
  • restore integration tests
  • restore manual implementation of codegen shortfall
  • fix typo in description of createResource operation
• update dependencies, fixup readme, start a .gitignore

[jmartin-sul]

filed an issue with the Swagger Codegen folks about the mis-generated model field names: https://github.com/swagger-api/swagger-codegen/issues/9841

[jmartin-sul]

also filed https://github.com/swagger-api/swagger-codegen/issues/9842 and a proxy for it in this repo (https://github.com/LD4P/sinopia_server/issues/120)