docs: fix docs warnings

Author: fschoenfeldt

lib/knigge.ex

@@ -36,7 +36,7 @@ defmodule Knigge do
         ]
       end
 
-  Differences between the versions are explained in [the Changelog](./CHANGELOG.md).
+  Differences between the versions are explained in [the Changelog](https://hexdocs.pm/ex_knigge/changelog.html).
 
   ## Motivation
 
@@ -190,7 +190,7 @@ defmodule Knigge do
 
   By default `Knigge` does as much work as possible at compile time. This will
   be fine most of the time. In case you want to swap out the implementation at
-  runtime - by calling `Application.put_env/2` - you can force `Knigge` to do all
+  runtime - by calling `Application.put_env/3` - you can force `Knigge` to do all
   delegation at runtime. As you might expect this incurs runtime overhead,
   since the implementing module will have to be loaded for each call.
 

lib/knigge/behaviour.ex

@@ -8,9 +8,8 @@ defmodule Knigge.Behaviour do
   It works whether the module is already compiled or still open, for which it
   uses `Module.open?/1`. If the module is still open it directly accesses the
   module attribute `:callback` by calling `Module.get_attribute/2` and then
-  using `Knigge.AST.function_spec_from_callback/1` to transform the AST into a
-  function spec, such as `{:my_function, 2}` which is being returned as a
-  Keyword list.
+  transforms the AST into a function spec, such as `{:my_function, 2}` which
+  is being returned as a Keyword list.
   """
 
   alias Knigge.Options