After #7010 we need to make sure all our documentation recommends NewClient. We should still retain some tests for Dial but the majority of them should probably be converted to use NewClient as well.

Tasks:

• Tests cases that don't rely upon Dial (tests for WithTimeout/etc should keep using Dial).
• In documentation, update from Dial to NewClient everywhere (note: this includes http://github.com/grpc/grpc.io)
• Update anti-patterns doc to discuss the differences between Dial and NewClient and also mention WithTimeout specifically in the existing section about Dial.