zipkin: fix span duration stats in zipkin realtime
 - fix bugs in span duration stats
 - add tests for monoid

RB_ID=378081
moved Kafka receiver to ThriftSpan

Signed-off-by: Jeff Smick <jeff@twitter.com>

RB_ID=391305
Updating install info for zipkin web

Signed-off-by: Jeff Smick <jeff@twitter.com>

RB_ID=391323
fix zipkin-example
sync oss
Update hbase version
Update zookeeper version
Fix HBase test dependency problem
Fix guava dependency
Move the guava-hack files into the directory with the zipkin-hbase tests
Add comment explaining why there is a shim
Prepend DefaultMavenRepository to the resolvers for zipkin-hbase