A direct instance of snip% is uninteresting. Useful snips are defined by instantiating derived subclasses, but this class defines the basic fucntionality.
In deriving a new snip class, these methods must be overridden to create a useful snip:
If a snip can contain more than one item, then the snip's count must be maintained as well.
To define a class of snips that can be saved or cut-and-pasted:
Creates a plain snip of length 1.