Elixir: Fix Enum example and rename "char list" to "charlist"

The charlist change is needed because all Elixir core is using the
"charlist" version. We also should use to keep consistency.

Also, to_char_list/1 is deprecated since Elixir 1.5.

elixir.md

@@ -59,7 +59,7 @@ users = [ "Tom", "Dick", "Harry" ]
 {: data-line="1"}
 
 ```elixir
-Enum.map(user, fn user ->
+Enum.map(users, fn user ->
   IO.puts "Hello " <> user
 end)
 ```
@@ -308,7 +308,7 @@ n = 12
 
 ```elixir
 n |> digits()         # → [1, 2]
-n |> to_char_list()   # → '12'
+n |> to_charlist()    # → '12'
 n |> to_string()      # → "12"
 n |> is_even()
 n |> is_odd()
@@ -317,7 +317,7 @@ n |> is_odd()
 ```elixir
 # Different base:
 n |> digits(2)        # → [1, 1, 0, 0]
-n |> to_char_list(2)  # → '1100'
+n |> to_charlist(2)   # → '1100'
 n |> to_string(2)     # → "1100"
 ```