Build fixes

[MichalKononenko]

No description provided.

[coveralls]

Coverage decreased (-0.007%) to 71.749% when pulling 5199592 on MichalKononenko:BuildFixes into 8118ab7 on QInfer:master.

[coveralls]

Coverage decreased (-0.007%) to 71.749% when pulling 5199592 on MichalKononenko:BuildFixes into 8118ab7 on QInfer:master.

[coveralls]

Coverage decreased (-0.007%) to 71.749% when pulling 5199592 on MichalKononenko:BuildFixes into 8118ab7 on QInfer:master.

[coveralls]

Coverage decreased (-0.007%) to 71.749% when pulling 5199592 on MichalKononenko:BuildFixes into 8118ab7 on QInfer:master.

[cgranade]

It's pretty critical to have qinfer.__version__ defined in released builds, so I'd like to figure out how to either fix the builds or fail gracefully if version.py isn't properly created by setup.py. (Possibly both.) For instance, we may be able to modify __init__.py similar to the following:

try:
    from qinfer.version import version as __version__
except ImportError:
    __version__ = '<unknown>'

That would break a few things based on version comparisons, but if one uses distutils.version.LooseVersion, that should still at least give somewhat sensible answers:

>>> LooseVersion('<unknown>') < LooseVersion('1.0')
False
>>> LooseVersion('<unknown>') > LooseVersion('1.0')
True

As for build breakages, I'm seeing some builds failing due to QuTiP 4.1 now requiring a C++ compiler, such that we do need to fix those builds, but is there a specific build that you saw break due to version.py?