2.1.0

Added

• Add support for numbering in heading as used at adr-tools:
  They are removed when generating the log.
  Fixes #23.

Changed

• Really using the format of "Keep a Changelog": Versions are indicated without prefix v.
  E.g., v1.0.0 is now 1.0.0.
  This is also the format supported by @sindresorhus's np.