Enh tests compat pytables 2.1
unfortunately on Debian systems we still have pytables 2.1; but it still would be nice to have pandas' unittests to pass with skips but without an error or failure -- major incompatibility is absense of blosc compressor.   This changes make those tests conditional on the version of pytables being at least 2.2 to test blosc

Got it-- I can merge this later tonight. Are you OK with packaging the 0.4.0 release with your patches? Doesn't strike me that a bugfix release should be necessary.
 sure -- I can absorb all those into a patch queue ;-)

> ## Got it-- I can merge this later tonight. Are you OK with packaging the 0.4.0 release with your patches? Doesn't strike me that a bugfix release should be necessary.
> 
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> Yaroslav Halchenko                 www.ohloh.net/accounts/yarikoptic
 Cherry picked these commits. Thanks!
