'use strict' and eval about classnames

[dcousens]

@daviferreira could we just avoid the use of use strict?
We can enforce most of the structuring properties of strictness through a linter.

[JedWatson]

I think we could take use strict out if it's causing trouble, or @daviferreira am happy to review your wrapper too if that solves the problem.

From what I understand, modern javascript engines are able to optimise certain code paths if they know a function is in strict mode, this may or may not be a major issue / benefit for classNames - unfortunately I'm not familiar enough with the inner workings to say for sure...

[dcousens]

@JedWatson this is apparently true, however I'd prefer to see some benchmarks before we just assume.