Previously, when using a StringScheme, the Kafka spout would always
output the Kafka messages in a field called "str"; in this pull request,
the constructor to StringScheme takes a parameter that can be used in
place of "str", with "str" remaining the default.
Previously, when using a StringScheme, the Kafka spout would always output the Kafka messages in a field called "str"; in this pull request, the constructor to StringScheme takes a parameter that can be used in place of "str", with "str" remaining the default.