pathHelpers: getPathVariants: Use os.path.expanduser() to replace ~
Don't create side-effects in asserts!
(Several asserts were calling lock.acquire(), which is poor form.)
Fixes #132.  Fixes #133.
fixed typo in filename
Merge pull request #134 from burgerdev/filename-correction

fixed typo in filename
Added OpSubRegion2
OpCompressedCache: fixed comment.
[OpLabelVolume] updated documentation, introduced new tests for threading and Output/CachedOutput behaviour
[OpLabelVolume] removed duplicate code
Added first cut of OpResize (2D/3D only)
OpResize: Support 5D data.
[OpLabelVolume] added test for correct blocking
cleanup.
OpResize: Added simple progress reporting, but won't be accurate for multiple threads.
jsonConfig: Added new pseudo-type for roi tuples.
submodules: updated pydvid
dvid operators use DvidConnection instead of HTTPConnection.
OpInputDataReader: Added SubVolumeRoi slot.
Added scikitClassifiers.py, which contains classifier operators with swappable implementation.
Defined classifier interface and replaced old RF classifierOperators with generic versions.
classifiers: Refactored again.  Distinction between 'classifier' abc and 'classifier factory' abc.