Couple of snippets and typos fixes

Hi,

Reading that document was really inspiring. You guys did a great job on that.
I made a few changes, some of them are fixes, and a bit of new things I thoght useful to be added.

First of all, there was an error on the expected output of the first snippet ([Primitives](https://github.com/Olivine-Labs/lua-style-guide#types)). The right output would be 1 and 9, instead of 1 and 2.

Second, for the [Complex type](https://github.com/Olivine-Labs/lua-style-guide#types) section, I thought it might be illustrative to highlight the fact that the assignment returns a reference to the same table. That is, creating a new key (0 here) makes that new field accessible from both references. But also, modifying an existing key results in the same. I expanded a bit the snippet regarding that.

Third, concerning the functions being small, I added a external link to a great blog post on the same topic I came accross in the past days, written by @kikito.

Last point, concerning the function syntax to be used to name functions, I am totally okay with that. Except that for the next example snippet (about the use of arg, deprecated in 5.1), that function syntax should be used in the example, in order to be consistent with what was said in the previous lines. I also fixed that.

The rest was all about random typos fixes, not much, actually.
And once again, nice work, guys.

Best regards,
Roland.