Updated the plan a bit
Added another menu button to stretch the menu a bit
Added a method to calculate the required size of the menu_container div
Merge branch 'dev-menu' into dev-menu-sexyMenu

Conflicts:
	src/menu_buttons.js
The menu buttons can be dragged left and right without restrictions
Added some basic limiting of horizontal scrolling
If you continue to drag when the menu is at one of its limits, dragging back will make the menu immediately scroll again
The menu buttons now fly (or glide) when swiped across
Tweaked constants a little
Can now swipe up/down to show/hide the menu
Made the lower/upper bound calculations for menu position be functions
Added a function to check if the menu slidy bit is within its bounds
The buttons in the menu now return to their bounds when out of them after swiping
Swiping now works again, setting the velocity to zero on dragEnd was causing a problem as dragEnd is fired as well as a swipe
Merge branch 'dev-menu-sexyMenu' into dev-menu