v0.3.1

Quick release to add a missing feature in boreal: tags and metadatas of matched rules were not available in the scan results.

Detailed changelog:

Boreal:

• Add rule metadata and tags in results of scans. Only the rule name and namespace was listed, which was an oversight.
  In addition, the Metadata and MetadataValue structs from boreal-parser are re-exported, to avoid having to depend on it to
  inspect matched rules metadatas.
  See PR #85.