Underscores not allowed in --kinesisendpoint

[cjbottaro]

Underscores should be allowed in hostnames.

Exception in thread "main" java.lang.IllegalArgumentException: kinesisEndpoint must match the pattern ^([A-Za-z0-9-\.]+)?$, got foo_nginx_1
	at com.amazonaws.services.kinesis.producer.KinesisProducerConfiguration.setKinesisEndpoint(KinesisProducerConfiguration.java:985)
	at com.disneystreaming.pg2k4j.CommandLineRunner.getKinesisProducerConfiguration(CommandLineRunner.java:237)
	at com.disneystreaming.pg2k4j.SlotReaderKinesisWriter.<init>(SlotReaderKinesisWriter.java:77)
	at com.disneystreaming.pg2k4j.CommandLineRunner.run(CommandLineRunner.java:25)
	at java.base/java.util.Optional.ifPresent(Optional.java:183)
	at com.disneystreaming.pg2k4j.CommandLineRunner.main(CommandLineRunner.java:45)