Add plugin to partition data by channel
Merge pull request #6 from mreid-moz/issue_916891

Add plugin to partition data by channel
Add docs about proposed "Process Incoming" arch

This is jonasfj's proposal from last week.
Merge branch 'master' of github.com:mreid-moz/telemetry-server
Merge branch 'master' into histogram_server
Serve either raw Histograms.json or bucket ranges.

Raw Histograms.json:      /histograms?revision=url
Histogram bucket ranges:  /histogram_buckets?revision=url