Add missing alembic upgrade step for stacks
masher: Add a MasherThread.cmd method
masher: Add an update_comps method (fixes #97)
ini: Update the comps_dir in our development config
tests: Isolate the update_comps call to a single unit test
tests: Ensure we git pull & make comps
bootstrap: Symlink in the libxml2 modules in order to build comps
masher: Make all !0 subprocess returncodes fatal
masher: Only log stdout if there is any
tests: Ensure non-zero subprocess returncodes raise exceptions
masher: PEP8 and docstrings
Merge pull request #98 from fedora-infra/feature/comps

Update/build the comps repo for mash