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
Added StartIndex and EndIndex to MessageTemplateToken
Use the new constructors when parsing
Added indexes to test tokens
Added more tests to improve coverage
Added missing XML docs
Removed EndIndex property
Made startIndex ctor argument optional
Brought net40 project up to par
Changed default value back to -1