Add tests for getUnitString
Simplify getUnitString
Add FileNotFoundError (from py3k) to test_whisper

Also move the caught exceptions around os.unlink() to be more explicit
Add skeleton TestReadHeader for whisper.__readHeader()
Be a bit more explicit about some struct unpacking exceptions
Refactor tests to remove some duplication
Fixing a weird edge case in whisper.py caught by testing

If you set whisper.CACHE_HEADERS to True and run whisper.info to
cache the headers, the cached version will always be used even if
whisper.CACHE_HEADERS is still used.
Updating code coverage for whisper.setAggregation
Improve test coverage of whisper.update
Update tests of whisper.merge for MOAR coverage

Once the coverage is a bit more up to spec, I can actually refactor
some of these bits and still sleep at night.
Add full coverage for whisper.parseRetentionDefs
Minor stylistic updates in whisper.py
Add back itertools

This was removed when I rebase removed my py3k support changes
as @brutasse opened #70 long before I had this all ready to merge.
Add small test for CorruptWhisperFile
Add initial tests for whisper.{file_,}diff

This ups the test coverage to 86% for whisper.py
Add a test for diff/file_diff with ignore_empty=True
Ensure that a result which doesn't raise an exception is validated
Pull in the coverall.io travis config changes

This lets us track the improvements in test coverage this branch
brings see this website for more information:
    https://coveralls.io/r/graphite-project/whisper
Merge branch 'master' into moar-tests
Add test for whisper.info() with a bogus file returning None