Add missing changes for 2.1 release

README.asciidoc

@@ -18,8 +18,8 @@ Cowboy is *clean* and *well tested* Erlang code.
 
 == Online documentation
 
-* https://ninenines.eu/docs/en/cowboy/2.0/guide[User guide]
-* https://ninenines.eu/docs/en/cowboy/2.0/manual[Function reference]
+* https://ninenines.eu/docs/en/cowboy/2.1/guide[User guide]
+* https://ninenines.eu/docs/en/cowboy/2.1/manual[Function reference]
 
 == Offline documentation
 

doc/src/guide/getting_started.asciidoc

@@ -69,7 +69,7 @@ fetch and compile Cowboy:
 PROJECT = hello_erlang
 
 DEPS = cowboy
-dep_cowboy_commit = 2.0.0
+dep_cowboy_commit = 2.1.0
 
 DEP_PLUGINS = cowboy