ixa-v0.3.0

This release makes a breaking change to data plugins. When migrating:

• Look for instances of of get_data_container and replace them with get_data
• Look for instances of get_data_container_mut; if they were purely for initialization of
  the data container, they can be removed or replaced with get_data.
  If a mutable reference is actually needed, replace with get_data_mut
• Look for instances of define_data_plugin; you may be able
  to move code that was previously outside of the macro into the initializer

Added

• [breaking] New data plugin API (#464)

Fixed

• Silenced a handful of warnings that are only emitted for the web_api feature. (#469)

Other

• Made the check for a request of zero sampled people more robust, which potentially avoids a panic deeper in the code path. (#474)
• enable markdownlint and ignore CHANGELOG.md (#462)