Strict configuration checking and readme update (#35)

* Don't allow unknown keys while deriving Pureconfig readers - avoiding misconfiguration.
Reimplemented `RecoveryDelayHandlerReader` to support the policy above.
* New convention - producers, consumers and declarations are wrapped into subconfigs
* Reordered field in config ccs to make more sense
* Better error tracking
* Readme update

Migration-6_1-8.md

@@ -1,20 +1,27 @@
 ## Migration from 6.1.x to 8.0.x
 
-Common changes:
 
-1. Additional declarations: `bindQueue` now has more consistent API. The only change is `bindArguments` were renamed to `arguments`.
-1. You are able to specify network recovery strategy.
-1. You are able to specify timeout log level.
+Java API was **COMPLETELY REMOVED** and won't be supported anymore. Checkout version 7.x for the last version supporting Java API.
 
-Changes in Scala API:
+---
 
 1. API is fully effectful.
     * Init methods return [`cats.effect.Resource`](https://typelevel.org/cats-effect/datatypes/resource.html) for easy resource management.
     * Declaration methods return `F[Unit]`.
-
-Changes in Java API.:
-
-1. You can specify `timeout` in the connection builder. It's used during initialization and closing of the client.
+1. Library could be configured with case classes - this is the default way. See [`RabbitMQConnection.make`](core/src/main/scala/com/avast/clients/rabbitmq/RabbitMQConnection.scala#L73).
+1. Configuration from [Lightbend `Config`](https://github.com/lightbend/config) was separated to [`pureconfig`](pureconfig) module. It's
+behavior remained backward compatible with these exceptions:
+    * SSL context is now passed explicitly and is **ignored** in `Config` (see more below).
+    * **You have to use `import com.avast.clients.rabbitmq.pureconfig._` to be able to use `fromConfig` method!**
+    * **Required structure of config has been changed** - all consumers must be in `consumers` block, producers in `producers` and additional
+    declarations in `declarations` blocks. See more info in [`pureconfig module docs`](pureconfig).
+    * It's required that the config doesn't contain anything else than configuration of the client. Presence of unknown keys will cause failure
+    of configuration parsing. 
+1. SSL is now configured explicitly in `make`/`fromConfig` method by passing `Option[SSLContext]`. Use `Some(SSLContext.getDefault)` for enabling
+SSL without custom (key|trust)store; it's now disabled by default (`None`)!
+1. You are now able to specify network recovery strategy.
+1. You are now able to specify timeout log level.
+1. Additional declarations: `bindQueue` now has more consistent API. The only change is `bindArguments` were renamed to `arguments`.
 
 ---