Included the missing code examples, as well as the excluded 'Examples' and 'Under the Hood' sections.  Additionally, made it more clear as to which methods are Relational Model type methods and which are instance methods.
Included the missing code examples, as well as the excluded 'Examples' and 'Under the Hood' sections.  Additionally, made it more clear as to which methods are Relational Model type methods and which are instance methods.

airbnb/Backbone-relational,xcambar/Backbone-relational,closeio/Backbone-relational,goodwall/Backbone-relational,xcambar/Backbone-relational,BothMedia/Backbone-relational,matghaleb/Backbone-relational,nikolas/Backbone-relational,GerHobbelt/Backbone-relational,closeio/Backbone-relational,PaulUithol/Backbone-relational,Feasul/Backbone-relational,Feasul/Backbone-relational,goodwall/Backbone-relational,leeleo26/Backbone-relational,nikolas/Backbone-relational,leeleo26/Backbone-relational,PaulUithol/Backbone-relational,matghaleb/Backbone-relational