Adding 'mousedown' & 'mouseup' for mobile.
'Shots' now starts/ends with touch events as well as mouse events.
Refactor functions 'startShots' and 'stopShots' functions.
Vars now exist for previously hard-coded sizes & durations.
Single shotglass image now uses same file as BG shots.
'dropSingles()' now includes comments for each step.
More concise comments in dropSingles().