add a UDF pair for simple random sampling with replacement (SRSWR)
merge datafu
Update file headers

[ci skip]
add copyright headers
minor updates to SRSWR
Merge branch 'master' of github.com:linkedin/datafu
Merge pull request #73 from matthayes/master

Add SetDifference, HyperLogLogPlusPlus, and improve tests
merge datafu
switch back to RandomDataImpl from commons-math-2.2
Add another SetIntersect unit test
update javadoc
more javadoc
Merge pull request #75 from matthayes/master

Remove requirement to include Guava JAR
Merge pull request #74 from mengxr/master

Add a UDF pair for simple random sampling with replacement (SRSWR).
Bumping datafu version to 1.2.0

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Rename files
Fix issue with collapsing job reusing output

When reusing output, the collapsing job subtracts off the oldest data from the previous result.  However, there were a couple problems:

1) When multiple days elapsed since the previous output, it didn't subtract the old inputs off correctly, yielding "negative" counts.
2) The job doesn't check whether it is beneficial to reuse the output.  If the window size is very small, then it may be better to consume the full window instead of reusing output.

This fixes both these problems.  When subtracting off data, it now only subtracts off data that was actually used in the previous result.  Also when considering reusing output, it compares the total bytes consumed to the total if the job didn't reuse output.

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Add execution planner test case

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Improve logging in collapsing execution planner

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Implicitly use end of range as path in tests

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Released hourglass 0.1.3, hence bumping version

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