Create 0.3.0 Release Notes (#872)

docs/release_notes/v0.3.0.md

+# Dapr 0.3.0
+ 
+We're happy to announce the release of Dapr 0.3.0.
+ 
+This release focused on improvements to our end-to-end tests infrastructure, making Service Discovery into pluggable components to support more hosting platforms, adding a few new components, improving CLI error messages and stability, and resolving bugs on and improving the Dotnet SDK.
+
+Visit the [getting started](https://github.com/dapr/docs/tree/master/getting-started) page to get started with Dapr.
+
+## Upgrading to Dapr 0.3.0
+
+To get the latest bits, follow the instructions [here](https://github.com/dapr/cli#installing-dapr-cli) to download the latest and greatest CLI release and binaries.
+
+Once you have the Dapr CLI in your path, run `dapr init`.
+Wait for the update to finish, and you're good to go!
+
+## Kubernetes
+
+If you previously installed Dapr on your Kubernetes cluster using the Dapr CLI, first download the latest CLI release as outlined above.
+
+Once you have the CLI, run:
+
+```
+dapr uninstall --kubernetes
+dapr init --kubernetes
+```
+
+If installed Dapr previously via Helm, run the following command to upgrade:
+
+```
+helm upgrade dapr dapr/dapr --set global.tag=0.3.0
+```
+
+*Note: If you installed with a different chart name, use `helm upgrade <your-chart-name>`*
+
+## Dapr Runtime
+
+**Decoupled** Service Discovery from the runtime by making discovery a pluggable component
+
+**Added** Couchbase as a State Store
+ 
+**Added** RabbitMQ as a Pub/Sub Message Bus
+ 
+**Improved** Error message for unsupported state store for actors
+
+**Improved** Go import statements
+
+**Improved** End-To-End tests infrastructure and helper utils
+
+**Added** End-To-End state management tests
+
+**Added** End-To-End bindings tests
+
+
+## CLI
+ 
+**Added** Flags to be presented as environment variables
+ 
+**Changed** Name of `send` command to `invoke`
+ 
+**Added** The ability to choose an installation path for Dapr binaries
+
+**Improved** Error message when Docker isn't running
+ 
+## .NET  SDK
+ 
+**Fixed** Unregister timer error
+
+**Added** Serialization of ReminderInfo and Timer
+
+**Added** Ability for actor type to be specified during registration
+
+**Changed** Stylecop.Analyzers to be a private dependency
+
+## Samples
+
+**Fixed** Hello World node sample hanging if a state store isn't enabled
+
+**Improved** Structure for Hello World and Hellow World Kubernetes
+