Conflicts:
	tests/test_code_gen.py

  - Test with all available libraries, plus automatically
    generated permutations.

- add some more automated cases
- add some comprehensive (slooow) tests

Collect the fixes from code_gen_cleanup

Code gen cleanup

  - Fix failing tests
  - Refactor a bit to simplify the code
  - Re-test on stdlibs of 2.6, 2.7, 3.3, 3.4, 3.5

  - infinity does not round-trip correctly under any version
  - with statement does not work correctly with some versions

  - Add function to return canonical text representation,
    and use it from assertion functions

  - Add function that compares ASTs rather than source code

- Remove parentheses where not necessary
- Use triple-quoted strings where it makes sense
- Add placeholder for function to do nice line wrapping on output
- Fix formatting in a few copyright messages

Spring cleaning

THIS REVISION WILL NOT WORK YET!

THIS COMMIT WILL NOT ACTUALLY WORK!!!

In addition to renames, misc.py was also copied into node_util.py

Yield fixes

It turns out the cheezy way I did yield fixes before was no good, because
it is legal to do (yield foo)(bar).

The new way always encloses yield statements in parentheses.  This is ugly,
and MAY not (I don't know) work on earlier versions, although it works fine
on 2.7.

Fixes and testcases for issue #27

non-call dictionary unpacking

revise coding style in matter of async variants of `def`, `for`, and `with`

Python 3.5 iterable unpacking and async syntax; idiomatic dictionary literals

The trailing comma-space that was previously output, while perfectly
legal in every way, is not what most human Python programmers would
write in most situations. We use the same slick idiom as the
`comma_list` method (iterating over the enumeration, but writing the
comma-space before the elements if the index is truthy, which zero is
not) to not put anything extra after the final key-value pair.

The changes codified in PEP 448 for Python 3.5 allow the
iterable- ("splat") and dictionary- ("double splat") unpacking arguments
to be used an arbitrary number of times in calls. As a result of this,
the starargs and kwargs attributes on some ast nodes have vanished,
their function superceded by ast.Starred objects in inside of `args` and
ast.keyword objects with a name of None inside of `keywords`,
respectively.