Docs & style.
Typealiases for ReducibleType types.
Use the typealiases a bit more widely.
Remove the collection parameter.

Conflicts:
	Traversal/Latch.swift
	Traversal/Signal.swift
	Traversal/SourceOf.swift
Style.
Return the reduce function instead of calling it.

This indirection works around from the present unavailability of
partial application to generic functions.
Use a label for SequenceType construction.
Rename a test.
Test equality against the sequence directly.
Bump Box for map() methods.
Multi-line formatting.
Style.
Style.
Implement map() over Memo.
Put Nil after Cons.
Add a const function.
Simplify & correct Stream construction from reducibles.
Test the iteration of effectful streams.
Stream is reducible.
Test Stream reduction.