Add Enum cheatsheet

Author: josevalim

lib/elixir/lib/enum.ex

@@ -256,10 +256,13 @@ defmodule Enum do
       iex> Enum.map(map, fn {k, v} -> {k, v * 2} end)
       [{"a", 2}, {"b", 4}]
 
-  However, many other enumerables exist in the language, such as `MapSet`s
+  Many other enumerables exist in the language, such as `MapSet`s
   and the data type returned by `File.stream!/3` which allows a file to be
   traversed as if it was an enumerable.
 
+  For a general overview of all functions in the `Enum` module, see
+  [the `Enum` cheatsheet](enum-cheat.html).
+
   The functions in this module work in linear time. This means that, the
   time it takes to perform an operation grows at the same rate as the length
   of the enumerable. This is expected on operations such as `Enum.map/2`.

lib/elixir/pages/anti-patterns/code-anti-patterns.md

@@ -496,7 +496,7 @@ defmodule Extract do
     end)
   end
 end
-````
+```
 
 ```elixir
 # URL query string according to with the planned format - OK!