small random forest documentation fixes
Improved libpython search. Now works inside a virtualenv, too.

1. Use HINTS instead of PATHS (other than PATHS, HINTS are searched
   before the system defaults)
2. Searching the default paths, too. Required inside a virtualenv.
added RandomForest constructor argument 'label_count'
vigranumpy RandomForest constructor: provide the list of labels rather than their number
vigranumpy.filters.distanceTransform3D(): added support for anisotropic data (fixes #139)
added NaN handling to RandomForest predict functions
added anisotropic distance transform for 2D
minor HDF5 fixes (reports by St. Meister und J.M. Gottfried)
increased tolerance for a few tests (reports by V. Hilsenstein and A. Metzler)
HDF5: enforce chunking when compression is requested
HDF5: make sure chunk size doesn't exceed shape
Tutorial eingefügt
tutorial source code
tutorial added
comments added
tutorial-section importan methods added
examples using multiarray
tutorial-images added
mirror boundaries fixed
important methods in tutorial added