Real procedure-arity impl.
Major progress on handling real racket programs.

- Handle regexp literals in the parser.
- Fake-handling of with-continuation-mark.
  (This will work for anything that doesn't try to retrieve
   the marks)
- Add a few more primitives.
  (Need real implementation of quotient/remainder)
- Add meteor test.
- Correctly remember what module we were last processing.

We can now load racket/cmdline successfully.
Fix translation for e-n-i?.
I *think* this is the right way to deal with \ sequences
test for the bug in #49

closes #49
test for W_Cons.tostring(). closes #47
Fix dependency errors.
Change up format of requires in the AST
NaNs appear in the AST as '+nan.0' not 'nan.0'
Properly read in 'nan' values from JSON
Higher recursion limit and fake unicode escapes
Fix issue with JSON parser consuming past the end of string literals
This only manifested when the object being parsed had multiple strings
Merge branch 'master' of https://github.com/samth/pycket
Remove UnicodeBuilder import
Move impersonators/chaperones to their own files
I should have done this from the start
Better handling of requires on the Python side
Stub for hashes in the expander
Better hash table stubs
Implement continuation marks.

Untested, but mostly typechecks.

I can't figure out what the current translation error is about.
Fix implementation of continuation marks.

Also, switch to using a linked list for storing key/value mark pairs.