update README for 0.4 release

Test PR to track down the travis CI self->map.size() == self->map_elts assert

These cpython tests are passing now

This caused the 'self->map.size() == self->map_elts' assert we saw sometimes on travis CI

Parser fix: call fclose

Misc pyxl2 perf improvements continued

Misc optimizations for pyxl2

Add a FileHandle class for c++-style raii on FILE* objects.

Also, add support for using the cpython parser for parsing
strings (still only in -X mode).

add doc to existed builtin function or method

Support building distribution packages

- Add a pyston micro version
- Move to the convention of "current version number is for the next release",
  instead of "previous release".  I think this is more standard?
- Get rid of our PYTHON_VERSION_MAJOR/MINOR/MICRO flags, and instead use CPython's
  versions.  We in theory had the ability to target different micro versions at
  runtime, but we never made use of this.  Having the two sets of flags isn't
  very sensible either.

Add support for using the CPython parser

That file doesn't have an include guard so it's tricky to get it working.

Not the actual memory blocks in it, but just the main metadata
object.  It contains pointers to other python objects; we could
potentially remove those pointers (looks like they are just for
reference counting) but for now just conservatively-allocate it.