fixing tests, making numbers be part of the build/ directory so we
don't get generative number structs
Merge branch 'new-world' of github.com:brownplt/pyret-lang into new-world

Conflicts:
	tests/test-images.arr
Merge branch 'new-world' of github.com:brownplt/pyret-lang into new-world
fixing more tests; all tests except ones related to
image-to-color-list now pass.  These aren't exhaustive tests and they
don't check the picture output, but rather just check that nothing is
undefined by mistake