Use relative imports in compiler package now that it is required.  (Should this go into 2.5 or should we do compiler.XXX?)

were some cases where an int was assumed.

Also had to change the string of the exception when dividing and int by zero.
Not sure what the best error message should be.  Currently
  5 / 0 yields the message: ZeroDivisionError: float division

That isn't entirely correct.  But I'm not sure what else to do.

Mention the builtins that Neal killed.

raw_input() -> input().  old input behavior is history (and test_builtin passes again).  It was failing due to future division.

- all classes are new-style (but ripping out classobject.[ch] isn't done)
- int/int -> float
- all exceptions must derive from BaseException
- absolute import
- 'as' and 'with' are keywords