Load environment specific settings files.

This means to resolve #104 by creating a system to automatically load settings by environment for each application running with choko, including the core.

**P.s.: this adds a new dependency to choko; lodash.** [Lodash](http://lodash.com/) is a toolset full of ready-to-use functions to work with arry, objects, inheritance, and so on. I believe we would sometime need a dependency like that, anyway. In this case, I'm using it to deeply merge multiple objects into a new one (settings), and none of the already available libraries worked to solve this; neither has Prana's util tools. By the way, my recommendation is that at least in Choko, if not in Prana, we make the custom util be a wrapper of lodash, but with our own custom methods attached to it.