Prevent slideout if touchY changes more than 40 pixels

[michaek]

This is a revision of #73, following from #225.

The intention is to detect scroll intent and prevent triggering the slideout when the touchX changes 20px, even when the body element does not scroll.

[coveralls]

Coverage decreased (-0.3%) to 7.143% when pulling 5266c1c on michaek:scroll-detection into 26fca60 on Mango:new-features.