More accurate space ratio

Detect the actual height:width ratio for spaces instead of guessing :)  Basically, it just creates a DOM element with only a nonbreaking space (at 2000px font-size to get the most accurate reading), inserts it for a split-second, measures it, then gets rid of it.  Improves accuracy pretty significantly and doesn't cost much.
@sreyemnayr This seems to work pretty well. This is a much more accurate estimate of space width which should cause the algorithm to work more efficiently.

I'll need you to clean up the code:
* In general, I like to have JSLint pass, so fix indenting
* Remove `// BEGIN CHANGE` and `// END CHANGE` comments
* I'd like to see this code put in a separate function to make code easier to read