rfc5051-0.2: changelog.md

# 0.2

  * Change API to use Text instead of String.
  * Add changelog.
  * Add test suite.
  * Move source to src directory.
  * Add Makefile.
  * Regenerate UnicodeData.hs module based on latest UnicodeData.txt.
  * Removed bytestring dependency.
  * Simplified dependencies on MkUnicodeData, removed unneeded Types module.
  * Remove MkUnicodeData flag and executable stanza.
    Easiest just to run this script with runghc.