Triangles can revert back to zero opacity

Triangles can revert back to zero opacity by clicking when at full
capacity
Triforces flash full fill color opacity when made
Paint triangles when mouse is dragged

Changed mouse interaction so that triangles are painted when mouse is
dragged instead of when mouse is moved. When a triangle reaches full
opacity, the ‘direction’ of painting can be flipped so that a triangle
can be depleted of opacity/erased. This flip requires that the mouse
drag event stops (a mouse up event is received). This is enforced so
that you can achieve perfectly full opacity without having to ‘time’
the ending of your drag.
Merge branch 'master-traffictype-mousemodes' into master-traffictype
Merge branch 'master-traffictype'
Painting speed, initial triangle size adjustments

Changed the initial triangle size and speed at which triangles are
painted in so that the sketch displays better on both a computer and an
A5-running iOS device
Merge branch 'master-traffictype'