add more cell strategies
uncomment some working strings in struct-test
uncomment old procedure with keyword args test for structs (it works now)
Merge branch 'master' of https://github.com/samth/pycket
Merge branch 'master' of https://github.com/samth/pycket
wrap mutable struct values (into W_Cell) in constructor
wrap mutable struct values (into W_Cell) in constructor (fix)
fix error in test_procedure_arity
remove string strategy from W_Cell (because strings are mutable)
`read` on lists, plus a more sensible (if recursive) implementation.
Refactor tokens to help fix translation (and for general sanity).
shuffle things around to make the unwrappers smaller

this should improve our executable size quite a bit, since generate *a
lot of* unwrappers
add subclass_unsafe for unsafe isinstance assertions

this will not generate quite as good code as the precise unsafe, but
should be better than being completely safe

also, it serves as documentation of the subclass_unsafe arguments to
make them better if I can think of a better technique
asin and acos
Add #:exists handling to call-with-output-file
Add some char properties
less duplication
Gah
expose asin/atan
`read` dotted pairs.

Related to issue #127.