Log Message:
update to 2.2
changes:
-new compressor called Blosc (speed-up)
-A new `tables.Expr` module (based on Numexpr) that allows to do
 persistent, on-disk computations on many algebraic operations.
-Support for HDF5 hard links, soft links and automatic external links
-Suport for 'fancy' indexing
-bugfixes