A first imperfect implementation of define_equality

* needs to be refactored (too much repitition and long functions)
* check Equitable in Ruby Facets
An implementation with `include DefineEquality`

* based on the equitable function in Ruby Facets
* modified naming
* added :class the default list of equality_accessors
Clean-up HISTORY and README
The equality_accessors can be set manually

* def equality_accessors ; [:to_s] ; end
* include DefineEquality # without arguments, just the module not a function
Version 0.0.6 (DefineEquality module and function)