Remove unused requires in TR
Fix with-type when used at the top-level

In some situations, with-type would fail to clean up its
state before reporting an error at the top-level.
change the number printed at the bottom of tally maze to be the board
index of the current board, not the initial board
Fix `infer-self-type` for depth overriden methods

When an overriden method implements a subtype of the superclass
type, sometimes the typechecker gets confused what the type should
be in the resulting class type.
Port the slidey game to Typed Racket.

Work done by Earl Dean.
Avoid trying to check dependencies for planet packages.
change eq? to object=? in snip implementation
use object=? instead of eq? to handle contracted objects
better object=? handling