Release PHP 7.1 layer version 4

Author: txase

README.md

@@ -9,7 +9,9 @@ This is an early iteration of the PHP runtime Layer which is not yet ready for p
 ## Current Layer Version ARN
 When creating/updating a Lambda function you must specify  a specific version of the layer. This readme will be kept up to date with the latest version available. The latest available Lambda Layer Version ARN is:
 
-**arn:aws:lambda:\<region\>:887080169480:layer:php71:3**
+**arn:aws:lambda:\<region\>:887080169480:layer:php71:4**
+
+See [Releases](https://github.com/stackery/php-lambda-layer/releases) for release notes.
 
 ### Usage
 #### General Usage
@@ -92,7 +94,7 @@ Resources:
       Timeout: 30
       Tracing: Active
       Layers:
-        - !Sub arn:aws:lambda:${AWS::Region}:887080169480:layer:php71:3
+        - !Sub arn:aws:lambda:${AWS::Region}:887080169480:layer:php71:4
       Events:
         api:
           Type: Api