Expand travis matrix for 5.2 to match 5.1

Author: JonRowe

.travis.yml

@@ -71,20 +71,24 @@ matrix:
       env: RAILS_VERSION=5-0-stable
     - rvm: 2.3.7
       env: RAILS_VERSION=5.1.0
+    - rvm: 2.3.7
+      env: RAILS_VERSION=5.2.0
     - rvm: 2.4.4
       env: RAILS_VERSION=master
     - rvm: 2.4.4
       env: RAILS_VERSION=5-0-stable
     - rvm: 2.4.4
       env: RAILS_VERSION=5.1.0
+    - rvm: 2.4.4
+      env: RAILS_VERSION=5.2.0
     - rvm: 2.5.1
       env: RAILS_VERSION=master
     - rvm: 2.5.1
       env: RAILS_VERSION=5-0-stable
     - rvm: 2.5.1
       env: RAILS_VERSION=5.1.0
-    - rvm: 2.4.2
-      env: RAILS_VERSION=5.2.0.rc1
+    - rvm: 2.5.1
+      env: RAILS_VERSION=5.2.0
   exclude:
     # 3.0.x is not supported on MRI 2.0+
     - rvm: 2.0.0