BF+TST: Allow slight variation in DICOM orientation/spacing.

The Image OrientationPatient and PixelSpacings values can have
slight numeical differences (particulaly GE scanners). Use an
np.allclose test instead of straight equaulity.

Also fix the TestIncongruentImage test class, which was pretty
broken.
CLN: Cleanup trailing whitespace. Some cleanup done in last commit
BF: Allow group_by keys to be tested with np.allclose

Allows us to have ImageOrientationPatient in the group_by list
(allows localizer series to convert to multiple stacks), while
still grouping slightly different ImageOrientationPatient values
into the same stack.

Should fix Issue #24 (in combination with commit 172f1b1).
ENH: Increase allclose threshold in DicomStack.

Now matches the threshold used elsewhere (parse_and_group and
nibabel).
ENH: Add __version__ attr to package and --version option in CLI

Added info.py with relevant info for setup.py (like version). Also
added more info to the setuptools.setup call.
BF: Only use translators if we have seen their PrivateCreator.
Merge remote-tracking branch 'upstream/master'