Print stratosphere version also in YARN-mode in the JM log file
disable the MatchJoinCancelingITCase test to speed up travis builds
Add javadocs documentation to user-facing classes.
Add Writable interface to allow seamless support for Hadoop types
Reduce minimum memory threshold for sorter
Added direct array serializers for all primitives
Fix deep copy code in GenericArraySerializer
TupleComparator fixed

uses values of passed keys
can skip parts of the tuple if necessary
Add test for generic array serializer
Avoid unnecessary exception wrapping in PackagedProgram invokation.
Add TupleSerializer tests.
Improve TupleComparators.
Add a compare method to teh comparators that works directly on objects.
Fix bug in tuple comparator (state)
Rename UnilateralSortmerger -> ExternalSorter (part 1)
Fix checkstyle warning.
Add utility test to check string and tuple sorting (not active by default, time consuming and Linux OS dependent)
Fix checkstyle warning for Writable
Adjusted TupleTypeInfo for updated comparator
Tests for tuple and base type comparators
Add serializer for primitive char array
Primitive type arrays have dedicated serializers now.
Adjusted TupleComparatorTests
Fix javadocs in CsvReader