A PyTables wrapper

This is a PyTables wrapper that we wrote for a project. It does lots of things, but as a high-level summary you get:
- A dictionary-like interface for file objects where keys are HDF5 node paths
- Normal/Chunked/Extendable arrays
- Dictionary nodes: Uses a file node to store serialized dictionary objects. Additionally, any numpy arrays which are contained in a dictionary will be written to standard array nodes.
- Table nodes: Storage for structured arrays. Multidimensional columns are allowed.
- `os.makedirs`-like automatic creation of groups when adding nodes
- Easy attribute access through an `attrs` object on every node