Almost done with nulls. Found a bug related with detection of if the bit field is present in subschemas. To be solved.
Nulls support for Pangool :-)
Merge remote-tracking branch 'origin/master'

Conflicts:
	core/src/test/java/com/datasalt/pangool/tuplemr/mapred/TestComparators.java
	examples/src/main/java/com/datasalt/pangool/examples/avro/AvroTopicalWordCount.java
Nulls support for Pangool :-) Updated Changelog.