expr: add keepdims kwarg to Reduction
numpy: handle keepdims in reductions
raise ImportError when SparkSQL uses old-style classes

These don't play well with multipledispatch
import spark and sparksql separately
add spacing and period to sparksql error message
move sqlcontext old-style-class check in if pyspark check
keepdims fix in docs
Merge pull request #741 from mrocklin/guard-sparksql-imports

raise ImportError when SparkSQL uses old-style classes
Merge pull request #737 from mrocklin/keepdims

Add keepdims kwarg to Reduction
lean optimize on head
Add available_memory
into(str, ...) accepts dshape kwargument
Hard as bcolz dep for psutil
into(bcolz) guards against extra kwargs
lean: fix head optimization
Merge pull request #744 from mrocklin/optimize

 Optimize framework
typo
Merge pull request #740 from mrocklin/lean-projections

Optimization to insert Projections
Merge remote-tracking branch 'upstream/master' into mrocklin-optimize-bcolz
Merge pull request #751 from mrocklin/into-dshape

tiny fixes for into bcolz with dshape info