2.0.0

Added

• Overrides for most dunder methods called on tail_call(...).

Changed

• nested call mode has now been renamed to feature set.
  There is the base and full feature set.
  The full feature set enables nested tail calls and dunder overrides.
• tail_call(...).__repr__ no longer pretty prints a string relating to the tail call.
  Use tail_call(...)._to_string() to pretty print tail calls.