Update ruby versions in ci

Author: ianks

.travis.yml

@@ -2,14 +2,14 @@ language: ruby
 
 rvm:
   # start with the latest
-  - 2.5.0
+  - 2.5.1
   - jruby-9.1.17.0
 
   # older versions
-  - 2.4.3
-  - 2.3.4
-  - 2.2.7
-  - 2.1.9
+  - 2.4.4
+  - 2.3.7
+  - 2.2.10
+  - 2.1.10
   - 2.0.0
   - 1.9.3
 
@@ -33,7 +33,7 @@ branches:
 matrix:
   fast_finish: true
   include:
-    - rvm: 2.3.4
+    - rvm: 2.3.7
       jdk: oraclejdk8
       env: COVERAGE=1
   allow_failures: