Parsley 4.2.0-M2

This is the second milestone release ahead of the 4.2.0 release. This release enforces deprecations on existing combinators, which have all be enforced for this milestone. The remaining milestones and release candidates in this series are expected to be stable within minimal binary disruptions. The progress and any migration can be tracked at #145.

What's Changed

• Error pattern combinators by @j-mie6 in #148

Full Changelog: v4.2.0-M1...v4.2.0-M2