First cut on a Serilog integration.

Need to figure out disposal of correlationProperty.
Note: Test project upgraded to .NET 4.5
Updated method summaries
Added Rebus.Serilog.nuspec
Fixed adding properties to Serilog
Updated to Serilog 1.3.1
Switched to MessageContextEstablished
Merge branch 'feature-serilog' of https://github.com/fritsduus/Rebus into feature-serilog
added entry to changelog for serilog logger
Implemented a PostgreSql provider
Broke some files, reverted them
Merge https://github.com/hagbarddenstore/Rebus into feature-postgres

Conflicts:
	src/Rebus.Tests/App.config
	src/Rebus.Tests/Rebus.Tests.csproj
	src/Rebus.sln
	src/packages/repositories.config
made postgres tests pass
added contract tests for Postgres persisters
fixed sql concurrency inner exceptions for SQL and Postgres saga persisters
fixed postgres nuspec
updated changelog
ran the build script.... :)
Merge branch 'master' into rabbit-exchange-per-type