added documentation on serialization support (#177)

* fixed emperror url format

* added serialization documentation

Author: Guy Baron

README.md

@@ -23,6 +23,8 @@ A lightweight transactional message bus on top of RabbitMQ supporting:
 7) [Structured logging](https://github.com/wework/grabbit/blob/master/docs/LOGGING.md)
 8) Reporting [Metrics](https://github.com/wework/grabbit/blob/master/docs/METRICS.md) via Prometheus
 9) Distributed [Tracing](https://github.com/wework/grabbit/blob/master/docs/TRACING.md) via OpenTracing
+10) [Extensible serialization](https://github.com/wework/grabbit/blob/master/docs/SERIALIZATION.md) with
+default support for gob, protobuf and avro
 
 ## Stable release
 the v1.x branch contains the latest stable releases of grabbit and one should track that branch to get point and minor release updates.

docs/LOGGING.md

@@ -50,7 +50,7 @@ func SomeHandler(invocation gbus.Invocation, message *gbus.BusMessage) error{
   }
 ```
 grabbit makes it easier handling these cases and reduce the repetitive task of logging
-these custom contextual attributes in cases of errors by integrating the [emperror errors package] (https://github.com/emperror/errors).
+these custom contextual attributes in cases of errors by integrating the [emperror errors package](https://github.com/emperror/errors).
 emperror drop-in replacement for the default errors package allows developers to add the needed contextual data on the error instance and have graabit log the error with all contextual attribute.
 
 ```go

docs/SERIALIZATION.md

@@ -0,0 +1,35 @@
+# Serialization
+
+grabbit supports out of the box three serializers to format messages over the wire
+
+- gob (defualt)
+- protobuf
+- avro (experimental)
+
+To configure a bus to work with a different serializer than the default one you must call the WithSerializer function call on the builder interface passing it an instance of a gbus.Serializer.
+
+The following example configures the bus to work with the protobuf serializer
+
+```go
+package main
+
+import (
+	"github.com/sirupsen/logrus"
+	"github.com/wework/grabbit/gbus"
+	"github.com/wework/grabbit/gbus/builder"
+	"github.com/wework/grabbit/gbus/serialization"
+)
+
+logger := logrus.New()
+	bus := builder.
+		New().
+		Bus("rabbitmq connection string").
+		WithLogger(logger).
+		WithSerializer(serialization.NewProtoSerializer(logger)).
+		WorkerNum(3, 1).
+		WithConfirms().
+        Txnl("mysql", "database connection string").
+        Build("your service name")
+
+```
+