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Fixes #3

Let me know anyway I can improve! I still feel like I'm learning 'the functional way' so any feedback is appreciated.


The guide has a small section on `iodata`/`chardata`[1], @josevalim perhaps this could extended to show an example of concatenation and why it can be efficient?

[1] http://elixir-lang.org/getting_started/12.html#toc_5.