Conflicts:
redex-curnel.rkt
With names finally fixed, many more tests can actually run.
* Changed uses of case to eliminators
* Fixed uses of new case* macro
* Fixed some assorted bugs in reduction of eliminators
* Added capture-avoiding substitution
* Added equivalence during typing checking, including α-equivalence and
limited β-equivalence
* Exposed better typing-check reflection features to allow typing
checking modulo equivalence
* Tweaked QED macro to use new type-checking reflection feature.
* Fixed some test cases
