added tests for syslog parsing to pipeline/decoders_test.go
added a syslog_decoder based on the grok patterns from logstash
extended the SandboxDecoder so you can configure a post-processing step to decode timestamps properly.
added docs for the SandboxDecoder's timestamp extensions
added syslog_decoder.lua to the install list in CMake
added documentation for the syslog_decoder.lua sandboxdecoder
updated to use new Decoder API that returns a slice of packs and an error