Add reproduction of #16
Merge branch '2.4'
merge test
Hmmh. backport missing test changes
Merge branch '2.4'

Conflicts:
	src/test/java/com/fasterxml/jackson/dataformat/avro/RoundtripTest.java
comment out failing tests that will only be fixed in 2.5
Merge branch '2.4'

Conflicts:
	src/main/java/com/fasterxml/jackson/dataformat/avro/ser/ObjectWriteContext.java
	src/test/java/com/fasterxml/jackson/dataformat/avro/RoundtripTest.java
Minor improvements to failure handling