Merge remote-tracking branch 'upstream/master'

.travis.yml

README.md

accumulo/pom.xml

accumulo/src/main/java/com/yahoo/ycsb/db/AccumuloClient.java

...o/src/main/java/com/yahoo/ycsb/db/ZKProducerConsumer.java

aerospike/README.md

aerospike/pom.xml

...pike/src/main/java/com/yahoo/ycsb/db/AerospikeClient.java

bin/ycsb

binding-parent/datastore-specific-descriptor/pom.xml

...main/resources/assemblies/datastore-specific-assembly.xml

binding-parent/pom.xml

cassandra/pom.xml

checkstyle.xml

core/CHANGES.md

core/pom.xml

...c/main/java/com/yahoo/ycsb/measurements/Measurements.java

...main/java/com/yahoo/ycsb/measurements/OneMeasurement.java

...m/yahoo/ycsb/measurements/OneMeasurementHdrHistogram.java

.../com/yahoo/ycsb/measurements/OneMeasurementHistogram.java