Added a serializable wrapper for HyperLogLog
Added a countDistinct method to RDD that takes takes an accuracy parameter and returns the (approximate) number of distinct elements in the RDD.
Added countDistinctByKey to PairRDDFunctions that counts the approximate number of unique values for each key in the RDD.
Added dependency on stream-lib version 2.4.0 for approximate distinct count support.
Fixed document typo
Improved code style.
Added stream-lib dependency to Maven build
Made SerializableHyperLogLog Externalizable and added Kryo tests
Removed superfluous abs call from test cases.
Using origin version
Renamed countDistinct and countDistinctByKey methods to include Approx
Added stream 2.5.1 jar depenency
Added Java API for countApproxDistinctByKey
Added Java API for countApproxDistinct
Added Java unit tests for countApproxDistinct and countApproxDistinctByKey
minor improvements
Made the code more compact and readable
Merge pull request #73 from falaki/ApproximateDistinctCount

Approximate distinct count

Added countApproxDistinct() to RDD and countApproxDistinctByKey() to PairRDDFunctions to approximately count distinct number of elements and distinct number of values per key, respectively. Both functions use HyperLogLog from stream-lib for counting. Both functions take a parameter that controls the trade-off between accuracy and memory consumption. Also added Scala docs and test suites for both methods.
restore core/pom.xml file modification
Merge pull request #314 from witgo/master

restore core/pom.xml file modification