Updated README's breaking change notice.

Updated the breaking change notice in the README to be clearer and link to the Getting Started Configuration wiki entry.

README.md

@@ -11,49 +11,9 @@ Checkout our [release notes](https://github.com/aws/aws-sdk-go/releases) for inf

**Release [v0.10.0](http://aws.amazon.com/releasenotes/xxx) introduced a breaking change to the SDK.**

Updates SDK to use `session.Session` when initializing service clients.
Service clients now require a session, which contains the SDK defaults
and any additional configurations you've provided. This also allows you
to create a default set of request handlers for all service clients
created with a session. Enabling you to share configurations explicitly.

Migrating to this change you'll need to add a `session.Session` to your
application. The session will be used in each place a service client is
created. Naively this can be `s3.New(session.New())` instead of the
previous `s3.New(nil)`. If the `aws.Config` value was being passed in to
the service client the code would become, `s3.New(session.New(), cfg)`.
If you used `default.DefaultConfig` you can replace this logic with a
new session and set merge in the config which was beign set to the
global default value. Like `session.New(myCfg)` or:
Updates SDK by adding `session.Session` replacing the global `defaults.DefaultConfig`. A session is used to store configuration and request handler settings for service clients. Each service client's `New` function now takes a session as the first parameter, and an optional `aws.Config`, which will be used for the specific client instance being created.

```go
sess := session.New()
sess.Config.LogLevel = aws.LogLevel(aws.LogDebug)
```

Examples:
```go
    // Create a session with the default config and request handlers.
    sess := session.New()

    // Create a session with a custom region
    sess := session.New(&aws.Config{Region: aws.String("us-east-1")})

    // Create a session, and add additional handlers for all service
    // clients created with the session to inherit.
    sess := session.New()
    sess.Handlers.Build.pushBack(func(r *request.Handlers) {
        // Log every request made and its payload
        logger.Println("Request: %s/%s, Payload: %s", r.ClientInfo.ServiceName, r.Operation, r.Params)
    })

    // Create a S3 client instance from a session
    sess := session.New()
    svc := s3.New(sess)

    // Create a S3 client with additional configuration
    svc := s3.New(sess, aws.NewConfig().WithRegion("us-west-2"))
```
See the [Getting Started Configuration](https://github.com/aws/aws-sdk-go/wiki/Getting-Started-Configuration) wiki for more information on how to use sessions within your application.

## Caution