Lint jmxfetch and sort the list of JMX checks.
Add a kafka check, pulling metrics from JMX.
Use single quotes in kafka YAML to make it more readable
created MetricsBucketAggregator that aligns the Metrics into buckets the length of the interval before aggregating
update cassandra url
Fix kafka metric types and names.
move calculations to flush(); make Gauge report bucket boundary as timestamp; add tests
Merge branch 'master' of github.com:DataDog/dd-agent into statsd_buckets

Conflicts:
	.travis.yml
clean up pylint warnings
Collect metadata from Google Compute Engine instances
Fix Cassandra link for travis
Fix cassandra location
Skip Elastic search test for now

See #825
changed method of continuing empty counters; buckets are flushed with timestamp of the beginning of the bucket
dogstatd interval changed to 2 sec. separate aggregator interval (bucket size) from dogstatd interval (how often flush is called)
fix for intermittent test failure
elasticsearch: monitor cluster status

changes in cluster status currently generate events, but i would like to
generate custom alerts (with custom notifications) as well. this adds the
metric i would alert on.
Fix ES broken metrics with new ES version (issue #825)
Adding checks depending on Travis ES version
add check to track kafka consumer metrics