Minor documentation fixes

chain.go

diff --git a/chain.go b/chain.go
index 6f11eab..7c17aa5 100644
--- a/chain.go
+++ b/chain.go
@@ -1,17 +1,25 @@
+// Package alice provides a convenient way to chain http handlers.
 package alice
 
 import "net/http"
 
 // A constructor for a piece of middleware.
-// Most middleware use this constructor out of the box,
+// Some middleware use this constructor out of the box,
 // so in most cases you can just pass somepackage.New
 type Constructor func(http.Handler) http.Handler
 
+// Chain acts as a list of http.Handler constructors.
+// Chain is effectively immutable:
+// once created, it will always hold
+// the same set of constructors in the same order.
 type Chain struct {
 	constructors []Constructor
 }
 
-// Creates a new chain, memorizing the given middleware constructors
+// New creates a new chain,
+// memorizing the given list of middleware constructors.
+// New serves no other function,
+// constructors are only called upon a call to Then().
 func New(constructors ...Constructor) Chain {
 	c := Chain{}
 	c.constructors = append(c.constructors, constructors...)
@@ -19,13 +27,13 @@
 	return c
 }
 
-// Chains the middleware and returns the final http.Handler
+// Then chains the middleware and returns the final http.Handler.
 //     New(m1, m2, m3).Then(h)
 // is equivalent to:
 //     m1(m2(m3(h)))
 // When the request comes in, it will be passed to m1, then m2, then m3
 // and finally, the given handler
-// (assuming every middleware calls the following one)
+// (assuming every middleware calls the following one).
 //
 // Then() treats nil as http.DefaultServeMux.
 func (c Chain) Then(h http.Handler) http.Handler {