v0.9.0

Major Features and Improvements

• Adding functionality for handling structured data.

Bug Fixes and Other Changes

• StructStatistics.common_statistics changed to
  StructStatistics.common_stats to agree with Facets.

Breaking changes

• The change from StructStatistics.common_statistics to
  StructStatistics.common_stats may break code that had this field set and
  was serializing to some text format. The wire format should be fine.