Merge pull request #29 from folone/topic/hdf5

Plugged the leak in readGroupNames method.
Extended hdf5 reading group names test
Added additional types available for serialization to HDF5, while keeping pandas-readable
Minor doc fix
Merge pull request #30 from TreyLawrence/master

Minor doc fix
Working toward supporting nested paths
Made nested levels within hdf5 work
Fix missing pytables header on new file creation