Fix tooltip type
Minor comment wording fix
Add contracts for synchronizable events
Fix a private/augment method issue
Add support for inherit-field
Improve error messages for superclass checks

Also add a test for the inherit-field case for this
Use lists as sets for type-checking classes
Some progress on type-checking world.rkt

NOTE: DOES NOT COMPILE
Had to reorder definitions due to TR limitations

Use of an identifier with a type annotation later cannot
be type-checked if it's in a definition body, e.g.

  (define a (foo 3))
  (: foo (Integer -> Integer))
  (define (foo x) ...)

Note: does not compile yet
Add a typed 2htdp/image
Add an initial version of typed htdp/image
Doc fixes in 2htdp/image
Doc fixes in htdp/image
Type-check check-aux
Export struct type descriptors needed for typing

Note: merge this into the master branch if people
      are okay with it. Otherwise needs rethinking.
Progress on world

Note: still doesn't typecheck
Add more struct reflection functions into base-env

Many of these lack useful filters
Improve typed image
More GUI typing

Fixup later
Contract generation for events