Swap NEST for Elasticsearch.Net
Additional extension methods for configuring the Elasticsearch sink

- Added ability to use a connection pool by passing a collection of URIs

- Added overload that exposes the Elasticsearch.Net
  ConnectionConfiguration for full control of the connection to
  Elasticsearch
Build up bulk payload using a dictionary instead of string
Rename ESPropertyFormatter -> ElasticSearchPropertyFormatter
Merge branch 'master' of https://github.com/gmarz/serilog into gmarz-master
Merge branch 'gmarz-master'
Changelist