Removes need for global numManipulator var?
Made number manipulator placement function
Makes manipulator toggle more robust

- Makes sure mouseOn always gets a value. I should add a console
log for incorrect input too
A vauge error message for toggleNumManipulator
Whitespace and comments
Adds arrows and attribution, needs fix and style choices

- Number manipulator sticks around, I know how to fix it
though
- Style isn't great, but I need the other context for it
- Right now hovering on an arrow changes color which will
probably cue people to click it, but not to drag
- The number manipulator is centered under the whole number
span, which looks weird when there's a negative number sign
- Should also add alt and such to arrow images
Better file name, fiddling with size
Fixes number manipulator sticking around and takes out error msg

- There's lots of times when neither of the conditions are met
and it's not an error. Not sure how to handle those exactly or
to produce a proper error message
- Idea: To make it more clear that it's click and drag, add a
a line between the two arrows
Fiddled with arrow image, only good at certain zooms