Date formatted index names are a common pattern in Elastic setups. This
commit as a config field to specify a string pattern for index names.
The pattern is searched for sequenences inside {curly braces} and passes
any text found plus the current time through the Go time formatting function.
This new sink adds basic support for Kafka, using `sarama.SyncProducer`.
It allows minimal configuration to make it useful:
- Topic
- Broker List
- TLS settings
The layout transformations are supported in the same way as for kinesis.
Implements issue #6.
Mustafa Akın
Dmitriy Kononov
shikloshi
Aaron Brodersen
aseker
Marc Demierre