H5SpecReader: Support SIMPLE HDF5 dataspaces as well (#80)

Some programs like Igor Pro always write SIMPLE dataspaces instead of
SCALAR ones. As we should not care about the exact type, we dig now
deeper if we find an array with just one element.

src/hdmf/backends/hdf5/h5_utils.py

@@ -163,6 +163,11 @@ def __init__(self, **kwargs):
 
     def __read(self, path):
         s = self.__group[path][()]
+
+        if isinstance(s, np.ndarray) \
+           and s.shape == (1,):
+            s = s[0]
+
         if isinstance(s, bytes):
             s = s.decode('UTF-8')
         d = json.loads(s)