Changelog for nominal-0.2.0.0

ChangeLog v0.2.0.0 2018/11/10 (2018/11/09) PS1 - documentation updates: added related works, acknowledgements, and references. Added a README file for bitbucket. (2018/11/09) PS1 - renamed Nominal.Generics as Nominal.Generic. (2018/11/09) PS1 - added type class instances for Ordering, Maybe, and Either. (2018/11/09) PS1 - renamed NominalPattern to NominalBinder, to avoid confusion between Haskell patterns and Nominal binders. (2018/11/09) PS1 - added abstraction patterns (:.). (2018/11/09) PS1 - removed unused open2 functions. v0.1.0.0 2018/11/08 Initial public release.