NServiceBus version 4 and RavenDB 2.5

If using NServiceBus v4 endpoints and RavenDB 2.5 server is installed, then the user must install the NServiceBus.RavenDB nuget package and initialize appropriately. Added Guidance. Fixes https://github.com/Particular/docs.particular.net/issues/158
Merge pull request #475 from Particular/issue-158

NServiceBus version 4 and RavenDB 2.5