[WIP] petsc4py build

I'm working on building petsc4py on a variety of platforms.  Since petsc4py's primary dependencies, PETSc and Python, represent two of our most challenging build environments, getting this right on our supported platforms is both a nice smoke-test and demonstration for <#>

To test this out on your own system:

```
git clone https://github.com/hashdist/hashdist.git
export PATH=${PWD}/hashdist/bin:$PATH
hit init-home
# see http://hashdist.readthedocs.org/en/latest/userguide.html for more details
git clone -b petsc4py-build https://github.com/hashdist/hashstack2.git
cd hashstack2
cp default.example.yaml default.yaml
# modify default.yaml to match your build environment, (currently Debian/SuSE)
hit build -v
./default/bin/python -c "from petsc4py import PETSc"
```

I'll try and throw some OS X and Cygwin #-builds up tonight.