Python module tables

Added the python module [tables](http://www.pytables.org/moin). It is an optional dependency to [pandas](http://pandas.pydata.org/pandas-docs/stable/install.html#optional-dependencies) for reading/writing hdf5 archives.

I've also added [numexpr](https://github.com/pydata/numexpr), which is a dependency for tables, and updated hdf5, and pandas.

I've added optional dependencies to hdf5. One is zlib, the other is szip. The former is required by tables.

Last, I fixed the source hash for szip.