v0.1pre12

What's Changed

• Updating README.md by @kjvbrt in #31
• Do not use GaudiAlg by @jmcarcell in #37
• Removing CentOs7 from build workflow by @kjvbrt in #38
• Use std::shared_ptr for compatibility with HepMC3 3.3.0 by @jmcarcell in #39
• Removing no longer needed casts by @kjvbrt in #33
• Saving filter stats to the metadata by @kjvbrt in #32

Full Changelog: v0.1pre11...v0.1pre12