Feature request: support JSONL

[dmoore247]

Nice tool, superior to avro tools for our json format.
New features: for conversion, maybe validate, support multi-line json (jsonl) formatted json files. See http://jsonlines.org/

For each json object, in json2avro mode, convert each json object to an avro object. Store just one avro schema in the file header.
Also clean up logging output, log to stderr or add output file option so we can capture the avro output.

cat 1000object.json | java -jar json-avro-converter-snapshot.jar --mode json2avro2json |wc -l
should produce 1000