Optimizations reduce run time by about 55%

Hey Josh - I've been using your string_score in a project and it's been tremendously helpful. My program makes enough comparisons that I needed to optimize things.

Apologies for changing the variable names. I am used to camelcase and needed it to think :)

On my machine, this optimization reduces a comparison from about 4.8 microseconds to 2.2 microseconds.