Fix name aliasing error.

The poll loop was closing whatever socket was last touched for
read/write, instead of the actual socket requesting to be closed.
Merge branch 'master' of github.com:rjpower/spartan
Add pagerank benchmark, update a few tests.
Nits related to parakeet generation.

Ensure parakeet source files are kept until the end of the program.
Disable parakeet for astype() calls.
Fix handling of keyword arguments.
Use cProfile to handle profiling of rpc poll loop handlers.

yappi seems to have trouble tracking these calls for unknown reasons.
Small optimization for fetching slices.

First fetch the individual slice pieces and determine their type
(masked, sparse or dense).  If all pieces are dense, then create
a dense array to hold the result, otherwise create a masked array.
Don't panic if the config file/directory can't be created.
Avoid creating a masked result if possible.
Switch back to cProfile based profiling for workers.

Add is_master() to blob_ctx; useful for logging.
Fix flag parsing for cluster flags.
Add pagerank benchmark.