Refactor compute function

- Simplify edge cases by passing an initialValue to reduce()
- Remove multiple method calls by doing an initial map()
- Inline getNum function
whitespace
Use convention for 'private' functions

Move them below public functions, also.
Move offsetting to convert method

Adding 1 is a consequence of the filenames currently being named 1-10,
and it seems more straightforward here.
Extract and name our reduce function

Takes a modulus and returns a summing function.
Install mocha and chai

Let's get out test on
Add Mocha options
Add reallll basic test