Adding ability to drag camera around
Setting width and height on canvas

The canvas will not render with the correct scale if the width and
height are not set on the canvas.
Adding rendering of grass tiles

There are four different "heights" and the field is randomly
generated at startup.
Adding method of queueing refreshes
Fixing scrolling bug

The canvas would still drag if you released the mouse outside of
the canvas.
Adding randomly placed sheep
Adding grass growing and eating

Yum, yum, yum!!! Too bad the sheep aren't smart enough to move...
Moving grass generation into generateGrass function

The generateGrass function now also makes sure that the grass does
not get longer than the GRASS_MAX_LEVEL at all. Previously it was
allowed to become anything less than GRASS_MAX_LEVEL + 1.
Added sheep movement

There are also a few bugfixes, such as a variable scoping issue
and a bug where the sheep did not draw at the correct location.
Cleaning up a bit

Doing a few renames, reorganizations, and variable declarations
for consistency. I also removed a few overly-broad functions.