Mention IEx.Options in IEx's doc

Author: alco

lib/iex/lib/iex.ex

@@ -90,6 +90,30 @@ defmodule IEx do
   It is possible to override the default loading sequence for .iex file by
   supplying the --dot-iex option to iex. See `iex --help`.
 
+  ## Configuring the shell
+
+  There is a number of customization options provided by the shell. Take a look
+  at the docs for the `IEx.Options` module.
+
+  The main functions there are `IEx.Options.get/1` and `IEx.Options.set/2`. One
+  can also use `IEx.Options.list/0` to get the list of all supported options.
+  `IEx.Options.print_help/1` will print documentation for the given option.
+
+  In particular, it might be convenient to customize those options inside your
+  .iex file like this:
+
+      # .iex
+      IEx.Options.set :inspect, limit: 3
+
+      ### now run the shell ###
+
+      $ iex
+      Erlang R16B (erts-5.10.1) [...]
+
+      Interactive Elixir (0.9.1.dev) - press Ctrl+C to exit (type h() ENTER for help)
+      iex(1)> [1,2,3,4,5]
+      [1,2,3,...]
+
   ## Expressions in IEx
 
   As an interactive shell, IEx evaluates expressions. This has some