Change the type of bindings from a list to a map

Maps make more sense because the keys are unique.

doc/src/guide/req.asciidoc

@@ -197,8 +197,6 @@ And any other combination.
 
 === Bindings
 
-// @todo Bindings should probably be a map themselves.
-
 Bindings are the host and path components that you chose
 to extract when defining the routes of your application.
 They are only available after the routing.
@@ -222,10 +220,7 @@ To retrieve everything that was bound:
 [source,erlang]
 Bindings = cowboy_req:bindings(Req).
 
-They are returned as a list of key/value pairs, with
-keys being atoms.
-
-// ...
+They are returned as a map, with keys being atoms.
 
 The Cowboy router also allows you to capture many host
 or path segments at once using the `...` qualifier.

doc/src/manual/cowboy_req.bindings.asciidoc

@@ -8,10 +8,10 @@ cowboy_req:bindings - Access all values bound from the route
 
 [source,erlang]
 ----
-bindings(Req :: cowboy_req:req()) -> [{Name :: atom(), any()}]
+bindings(Req :: cowboy_req:req()) -> cowboy_router:bindings()
 ----
 
-Return all bindings as a list of key/value pairs.
+Return a map containing all bindings.
 
 == Arguments
 
@@ -27,7 +27,7 @@ automatically converting numbers to integer).
 
 == Changelog
 
-* *2.0*: Only the values are returned, it is no longer wrapped in a tuple.
+* *2.0*: Only the values are returned, they are no longer wrapped in a tuple.
 * *1.0*: Function introduced.
 
 == Examples

doc/src/manual/cowboy_router.asciidoc

@@ -33,7 +33,7 @@ a 404 response otherwise.
 
 [source,erlang]
 ----
-bindings() :: [{atom(), binary()}]
+bindings() :: #{atom() => any()}
 ----
 
 Bindings found during routing.