base mixin for all the token implementations
abstract Str templateSource()
1) Split the name on periods; the first part is the name to resolve, any remaining parts should be retained. 2) Walk the context stack from top to bottom, finding the first context that is a) a hash containing the name as a key OR b) an object responding to a method with the given name. 3) If the context is a hash, the data is the value associated with the name. 4) If the context is an object and the method with the given name has an arity of 1, the method SHOULD be called with a String containing the unprocessed contents of the sections; the data is the value returned. 5) Otherwise, the data is the value returned by calling the method with the given name. 6) If any name parts were retained in step 1, each should be resolved against a context stack containing only the result from the former resolution. If any part fails resolution, the result should be considered falsey, and should interpolate as the empty string.