Comments and Questions

:rotating_light: Not intended to merge. :rotating_light: 

@gjtorikian Here's the initial comments and questions that I have.

I also think it'd be worth trying to break up the code in `env_replacements` into multiple functions that it can call. I would try to make it call other functions to give a bit more clarity and shape to the code.
I stole this from StackOverflow: http://stackoverflow.com/a/1726648/213345

I think the idea is that it doesn't generate a new memory address. Does that seem safe? The alternatives of array access with `strlen(str)-1` appear "undefined in the C standard."