Merge pull request #13 from matzew/travis_update

adding jdk 8 CI builds

.travis.yml

@@ -3,6 +3,8 @@ language: java
 sudo: false
 
 jdk:
+  - oraclejdk8
+  - openjdk8
   - openjdk9
   - openjdk10
   - openjdk11

api/src/test/java/io/cloudevents/CloudEventBuilderTest.java

@@ -61,7 +61,7 @@ public class CloudEventBuilderTest {
         simpleKeyValueEvent.getData().ifPresent(data -> {
             assertThat(data).isNotNull();
             assertThat(data).containsKeys("key1", "key2");
-            assertThat(data).containsValues("value1", "val2");
+            assertThat(data).containsValues("value1", "value2");
         });
 
         assertThat(simpleKeyValueEvent.getContentType().get()).isEqualTo(contentType);