more consistent and descriptive metric types

[dirkraft]

counterSum meterSum histogramCount timerCount

These all represent the counting aspect of the various metrics constructs. Align all the names. Since we are going to rename these things and so introduce a breaking change on anything dependent on this CloudWatch metric dimension, let's go ahead and clean up all the names.

• [ ] rename the dimension to metricAspect, the word "type" which currently names the dimension is just way too generic and has high probability of conflict
• [ ] rename counters (CloudWatch MetricDatum) to {codahale metric type}Delta: counterDelta, meterDelta, histogramDelta, timerDelta. (reconsider) n.b. the original names were based on the information available in the metrics objects
• [ ] rename histogramCount to histogramSamples, because that's what it actually is
• [ ] rename stats (CloudWatch StatisticSet) to {codahale metric type}Stats: histogramStats, timerStats
• [ ] update README table with these changes and also, not sure this is communicated as effectively as it could be

This should result in a MAJOR version change according to http://semver.org. So we can roll this up into a 1.0.0 release.

[dirkraft]

Notes to self: I will rewrite this in a more sane way in a concerted effort to come. They are still good notes for where I was thinking in the past