A start at a multi-version release pattern.

This commit moves everything that was in the kitchen/ source dir into a
new kitchen2/kitchen/ source dir.  Eventually, we'll merge the py3port
branch into a kitchen3/kitchen/ source dir parallel to it.

I added both source folders to ``MANIFEST.in`` so when we create a
tarball with ``python setup.py sdist``, **both** source directories will
be included -- kitchen2 and kitchen3.

When the user downloads and installs the package with ``pip install
kitchen``, it will download the tarball with both sources, unpack it,
and run the single setup.py.  setup.py has new logic in it now that will
detect if the user is running python2 - if it is, then it will install
kitchen from the kitchen2/ directory.  If they're running python3 it will
install kitchen from the kitchen3/ directory.

Note that, the imports for users do not change at all.  For both python2
and python3, kitchen can still be accessed with

```python
>>> import kitchen
```

This commit doesn't actually include any of the python3 bits, but it
stubs out one approach we could use which I'm submitting for feedback
and potential usage.
Add .gitignore.
Move docs into the kitchen2/ dir.
Copy in the kitchen3 source_dir from the py3port branch.
Make releaseutils.py work on both py2 and py3.
Copy tests into kitchen2/ and kitchen3/.
Try travis-ci tests.
Test switching tool.
Maybe bash needed for pushd/popd.
Go ahead and add the pycompat2* submodules to the kitchen3 source_dir to make things easier.
Merge branch 'feature/dist-toggle'

Conflicts:
	runtests.sh