Clearly mark chapters as being part of the "Mix and OTP" guide #834
Description
The chapters of the "Mix and OTP" guide are, no surprise here, part of the "Mix and OTP" guide and often depend on the previous chapters. When a google result brings you to one of the chapters this is not apparent though.
I would add a little note to the beginning of all chapters in the "Mix and OTP" guide, something like this
Note that this chapter is part of the "Mix and OTP" guide and depends on the previous chapters.
Maybe read the [TODO add link](previous chapter) or start reading from the [http://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html](first chapter) of the guide.
If you're interested in this I would create a pull request.