Issue #12 .d.ts file

@caleb.weeks I do have a couple places where "any" is still used, mainly the callback function bodies. Let me know if those should be something else. I also wanted to point out the function preprocess(path: string, details?: any): Object. the "details" parameter doesn't appear to actually be used in the function, but including it here since it does exist. Again, let me know if I should change the "any" to another type.