Get rid of our freeze and unfreeze functions because they're in pyrsistent now.
oh, and get rid of the tests too, of course
pyrsistent 0.5.0 is released
Merge pull request #704 from rackerlabs/remove-freeze-unfreeze

Get rid otter.util.fp.freeze/unfreeze because they're in pyrsistent now
metrics collection tests added

Split getting all metrics in separate function
Merge branch 'master' into metrics

Conflicts:
	otter/convergence.py