Updated README.md to reflect the need to add an index analyzer.

  * Add metricname analyzer to opentsdb index, keyword analyzer with lowercase filter
  * Change tsmeta_map.json to use metricname analyzer for metric/key/value names
  * Change uidmeta_map.json to use metricname analyzer for uid names
  * Replace TSMetaHack with TSMetaAugment utility function that generates the normal TSMeta JSON then adds our new fields to the JSON tree before serializing to a byte array