v2.0.0-alpha.23

New feature:

• runtime: Message options are now available in reflection
  information, see #35.
• plugin: Groups (deprecated proto2 feature) are now completely
  ignored, but should still be treated properly as unknown fields.
• runtime: BinaryReader.skip() supports WireType.StartGroup now.

Breaking changes:

• runtime: The MessageInfo interface requires the new "options"
  property.
• plugin-framework: IDescriptorInfo.isMessageField() no longer
  returns true for GROUP field type.