Merge branch 'export_cluster-wide_node_stats' of https://github.com/d…

…an-cleinmark/elasticsearch_exporter into dan-cleinmark-export_cluster-wide_node_stats

0.1.1: Add a handful of new counters for indexing and merging

* Added `indices_indexing_index_total`
* Added `indices_indexing_index_time_in_millis`
* Added `indices_merges_total`
* Added `indices_merges_total_docs`
* Added `indices_merges_total_size_in_bytes`
* Added `indices_merges_total_time_in_millis`

Update Makefile.COMMON to newest version