Simplified logic in slide response.

[oniietzschan]

I was going through the bump source code recently and saw an opportunity for a small readability improvement to the slide function. I think removing sx and sy makes it a tad easier to understand, hopefully you'll agree.

I also added --no-max-line-length so that the Travis build would pass. I think luacheck started getting upset about lines longer than 120 character since a commit was last made to this repo.

[coveralls]

Coverage decreased (-0.009%) to 96.429% when pulling ca27d8c on oniietzschan:shru-cleanup into 72d6b13 on kikito:master.

[pablomayobre]

No idea why coveralls is reporting a decrease in coverage, but this should affect that much.

Most likely is to the file size reduction, 2 lines being removed could result in a % decrease. The logic is fine and the simplification really help with readability.

I would totally merge this

[kikito]

Yes, this makes total sense, thanks a lot for cleaning up that piece of code!