Update PHP runtime versions (#53)

* Update PHP 7.1 runtime to 7.1.26

* Update PHP 7.2 runtime to 7.2.15

* Update PHP 7.3 runtime to 7.3.2
diff --git a/core/php7.1Action/CHANGELOG.md b/core/php7.1Action/CHANGELOG.md
index e4c119b..e9ad5c8 100644
--- a/core/php7.1Action/CHANGELOG.md
+++ b/core/php7.1Action/CHANGELOG.md
@@ -19,7 +19,7 @@
 
 ## Apache 1.13.0-incubating (next release)
 Changes:
-  - Update version of PHP to 7.1.25
+  - Update version of PHP to 7.1.26
 
 ## 1.0.3
 Changes:
diff --git a/core/php7.1Action/Dockerfile b/core/php7.1Action/Dockerfile
index 21b7afb..e10a166 100644
--- a/core/php7.1Action/Dockerfile
+++ b/core/php7.1Action/Dockerfile
@@ -15,7 +15,7 @@
 # limitations under the License.
 #
 
-FROM php:7.1.25-alpine
+FROM php:7.1.26-alpine
 
 RUN \
     apk update && apk upgrade && \
diff --git a/core/php7.2Action/CHANGELOG.md b/core/php7.2Action/CHANGELOG.md
index 8cd72d9..a740728 100644
--- a/core/php7.2Action/CHANGELOG.md
+++ b/core/php7.2Action/CHANGELOG.md
@@ -19,7 +19,7 @@
 
 ## Apache 1.13.0-incubating (next release)
 Changes:
-  - Update version of PHP to 7.2.13
+  - Update version of PHP to 7.2.15
 
 ## 1.0.2
 Changes:
diff --git a/core/php7.2Action/Dockerfile b/core/php7.2Action/Dockerfile
index a03f9dc..0c2016f 100644
--- a/core/php7.2Action/Dockerfile
+++ b/core/php7.2Action/Dockerfile
@@ -15,7 +15,7 @@
 # limitations under the License.
 #
 
-FROM php:7.2.13-alpine
+FROM php:7.2.15-alpine
 
 RUN \
     apk update && apk upgrade && \
diff --git a/core/php7.3Action/CHANGELOG.md b/core/php7.3Action/CHANGELOG.md
index 59b4bbb..5908adf 100644
--- a/core/php7.3Action/CHANGELOG.md
+++ b/core/php7.3Action/CHANGELOG.md
@@ -20,7 +20,7 @@
 ## Apache 1.13.0-incubating (next release)
 Initial release
 
-- Added: PHP: 7.3.1
+- Added: PHP: 7.3.2
 - Added: PHP extensions in addition to the standard ones:
     - bcmath
     - curl
diff --git a/core/php7.3Action/Dockerfile b/core/php7.3Action/Dockerfile
index a412851..240a357 100644
--- a/core/php7.3Action/Dockerfile
+++ b/core/php7.3Action/Dockerfile
@@ -17,7 +17,7 @@
 
 FROM openwhisk/actionloop:410d006 as builder
 
-FROM php:7.3.1-cli-stretch
+FROM php:7.3.2-cli-stretch
 
 # install dependencies
 RUN \