Vimap

- imap_ordered convenience function
- adjusted default spooling to be a little less. this is a little slower for
synthetic/test data, but helps avoid some IRL performance gotchas

- Minor change for setup.py -- printing warning to stderr

- Changed exception behavior so that zip_in_out() / imap_unordered()
re-throw exceptions from workers. If an exception couldn't be properly
serialized, then an alternate exception message is instead thrown.
- Fixed the queue manager's total in-flight calculation, not sure how this
will affect performance
- (from 0.1.9): Better bounds on queue sizes, which is helpful for expensive
input iterators

0.1.8-alpha-deadlock-quickfix (2014-07-31)
- Quick fix for a deadlock issue. See exceptions_test for the new test case.
Some other issues make me want to investigate more before this branch is
known to be stable.

- Added VimapFold and FileRunner convenience classes to ext.
This allows people to easily make vimap jobs that run over a bunch of files
in parallel and fold the output together

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- No longer specify testify in setup.py's install_requires. It is already
in requirements-dev and this prevents testify/mock from being installed
if you use vimap in production.

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- Prints full exception tracebacks when workers fail
- Removed stringification of worker kwargs (this caused issues when passing
large objects to workers, and was only done for debug purposes)
- Unit tests produce less console spam