Make tests.py into proper unit test, and add Qt version info to pytest header

[astrofrog]

Since I'm adding actual tests in #25 and #27, I thought it would make sense to formally switch over to using py.test to run tests. This also makes it so that the py.test header includes detailed Qt version information:

============================= test session starts ==============================
platform darwin -- Python 3.5.1, pytest-2.8.5, py-1.4.31, pluggy-0.3.1
benchmark: 3.0.0 (defaults: timer=time.perf_counter disable_gc=False min_rounds=5 min_time=5.00us max_time=1.00s calibration_precision=10 warmup=False warmup_iterations=100000)

PyQt4: PyQt: 4.11.4 - Qt: 4.8.7
PyQt5: not installed
PySide: not installed
...

[astrofrog]

This is now ready for review! (I think the quantifiedcode warnings can be ignored in this case)

[goanpeca]

Great work @astrofrog, :-)

[ccordoba12]

@astrofrog, thanks a lot for working on this! It's a great improvement :-)

@goanpeca, please disable QuantifiedCode.

[ccordoba12]

Is it possible to enter this part if we set always set USE_QT_API in travis.yml?

[astrofrog]

Not on Travis or AppVeyor, but it's possible if one runs the tests locally without specifying USE_QT_API or QT_API

[ccordoba12]

Ok

[astrofrog]

@ccordoba12 - do you need me to squash the commits? (not sure what kind of policy you use for qtpy compared to other projects)

[goanpeca]

@ccordoba12 the quantified code suggestions are valid

• Consider documenting your function(s)
• Avoid None as a redundant second argument to dict.get()

I will disable the one that complaints about having non pythonic method names which does not work when using Qt.

@astrofrog could you make the suggested "fixes"?

[ccordoba12]

Ok, I think this one is ready. We have to merge it with AppVeyor failing because there's no AppVeyor working at this point :-)