elastic/elasticsearch-net 2.5.1 on GitHub

Enhancements

#2484 Limit the number of concurrent connections on .NET Core, similar to Desktop CLR.
#2451 Small Performance improvements
Introduce a BufferSize property on JsonNetSerializer with a default size of 1024 to use when writing json to the request stream. Performance tests as part of #1899 indicate this to be a good compromise buffer size for performance throughput and bytes allocated.
#2495 Add important admonition (end of Simple Automapping section) to the documentation about the use of System.Decimal types as C# POCO properties

#2479 Deserialize "value_as_string" for metric aggregations that return it
#2466 Deserialize attachment title when deserializing an Attachment type from _source or field data
#2464 Add the StringEnumConverter to StringFielddataFormat to always serialize as string. Introduce coding standard unit test to assert the converter is applied to all NEST enums
#2487 Fix the virality of &= in the bool query DSL
#2496 Allow SourceFiltering.Disable to be set to false. This is synonymous with the default, which is to return _source in the response.

#2488Tidy up TODOs and make the usage of NotSupportedException consistent across all internal JsonConverter types.
#2486 Generate asciidoc files as part of the build