Improve/automatic width and height for subtitles

I think having the Private method exposure on the same field as the test would make more sense than putting it on other file. I guess the premise is that you should be able to figure out stuff by only looking at one file, or even one method, no need to jump or navigate to figure out this stuff.

I've been doing this in other places, has been working fine :)

https://github.com/hyperoslo/NSString-HYPFormula/blob/master/Tests/NSString-HYPFormula/NSString_HYPFormulaTests.m#L14