Allow zero-length selections
When slicing yields an empty array, return an emtpy array of the correct shape
Tests for slicing returning empty arrays
fixed tests of hdf5 <1.8.7

The datasets need to be created with unlimited maxsize
Merge pull request #1 from tacaswell/zero-length-selections

fixed tests of hdf5 <1.8.7
Merge upstream changes
Merge pull request #334 from khinsen/zero-length-selections

Slicing resulting in empty arrays