Add basic chicken view class.
Use image dims to set image world size

Restructure code so that the intrinsic image dimensions are used to
determine the image’s size in world coordinates, instead of hard-coding
the image world size. Update all tests, etc.
Move chicken drawing to the chicken view
Add basic egg graphics.
Add egg-count display.

Add the count of remaining eggs as a graphical display. Remove the
textual display of egg count.
Merge branch 'graphics'
Merge branch 'master' into gh-pages