Avoiding half-pixel translations.

Simple implementation of #883.
Note that the changed codes were meant to affect only the values that has to do with `translate` or `translate3d` in css, since the issue was about half-pixels in translations.
Related article: http://martinkool.com/post/27618832225/beware-of-half-pixels-in-css

p.s. Is it okay to submit only `slick.js` file? How should I treat with the `slick.min.js`?