Add the load of the races respository files.

The main idea here is add some convention to add new content data for races, items, character classes, backgrounds and etc.

I used a little bit of meta programming. XD
I added this quick fix to solve some tests issues.

But now I found the bug, my yaml "dump" was storing the array of items as symbols, and the hash keys are stored as strings. Everything should be stored as string. I'll fix the yamls and update the tests.