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Merge pull request #15 from thoop/patch-1

Update README.md to include your project status badge!
Updated tests to use level-test.
Ported benches to level-test.
Updated README to the new level depedency.
Merge branch 'levelup-v0.9' into v0.5.0

Conflicts:
	benchmarks/joinStream.js
	test/abstract_join_algorithm.js