use MultiJson.load and .dump in place of JSON.
deleting unused Gemfile.
renaming Binding#lambda_context to exec_context and making it private.
setter and getter methods are now called on the decorator (just as with lambdas) when representer_exec: true.
add json as dev dependency.
make Representable::Decorator::Coercion work.
rename :representer_exec to :decorator_scope. add docs to README about that now documented feature!!!
releasing 1.5.2.