add `dig` and `bury` options

[rerpha]

To dump/resend data from a topic and from a dump respectively.

    # saluki bury - dump data on topic to file
    # saluki bury mybroker:9092/topicname -p 0 -o startoffset finishoffset outputfile
    # saluki bury mybroker:9092/topicname -p 0 -t starttimestamp finishtimestamp outputfile

    # saluki dig - push data from dump generated by saluki bury to topic
    # saluki dig mybroker:9092/topicname -p 0 outputfile