chore(docs): use full path for message images

docs/messages.md

@@ -16,11 +16,11 @@ Pact is a consumer-driven contract testing tool, which is a fancy way of saying
 
 The process looks like this on the consumer side:
 
-![diagram](./diagrams/message-consumer.png)
+![diagram](https://github.com/pact-foundation/pact-js/blob/master/docs/diagrams/message-consumer.png)
 
 The process looks like this on the provider (producer) side:
 
-![diagram](./diagrams/message-provider.png)
+![diagram](https://github.com/pact-foundation/pact-js/blob/master/docs/diagrams/message-provider.png)
 
 1. The consumer writes a unit test of its behaviour using a Mock provided by Pact
 1. Pact writes the interactions into a contract file (as a JSON document)
@@ -156,4 +156,4 @@ describe("Message provider tests", () => {
 1.  Our API producer contains a single function `createDog` which is responsible for generating the message that will be sent to the consumer via some message queue
 1.  We configure Pact to stand-in for the queue. The most important bit here is the `messageProviders` block
     - Similar to the Consumer tests, we map the various interactions that are going to be verified as denoted by their `description` field. In this case, `a request for a dog`, maps to the `createDog` handler. Notice how this matches the original Consumer test. We are using the `providerWithMetadata` function because we are also going to validate message metadata (in this case, the queue the message will be sent on)
-1.  We can now run the verification process. Pact will read all of the interactions specified by its consumer, and invoke each function that is responsible for generating that message.
+1.  We can now run the verification process. Pact will read all of the interactions specified by its consumer, and invoke each function that is responsible for generating that message.