chore: update supported Java versions to match testing strategy

Author: Sam Harrison

.travis.yml

@@ -3,21 +3,14 @@ before_install:
   - echo $GPG_SECRET_KEYS | base64 --decode | $GPG_EXECUTABLE --import --batch || true
 matrix:
   include:
-    - jdk: openjdk7
-      dist: trusty
     - jdk: openjdk8
       dist: xenial
     - jdk: openjdk11
       dist: xenial
-    - jdk: oraclejdk7
-      dist: precise
     - jdk: oraclejdk8
       dist: trusty
     - jdk: oraclejdk11
       dist: trusty
-  allow_failures:
-    - jdk: openjdk7
-    - jdk: oraclejdk7
 install:
   - mvn --settings .maven.xml install -DskipTests=true -Dgpg.skip -Dmaven.javadoc.skip=true -B -V
 after_success:

CONTRIBUTING.md

@@ -49,7 +49,7 @@ We welcome direct contributions to the java-http-client code base. Thank you!
 
 ##### Prerequisites #####
 
-- Java version Oracle JDK 8 or OpenJDK 7
+- Java 8 or 11
 - Please see [build.gradle](https://github.com/sendgrid/java-http-client/blob/master/build.gradle)
 
 ##### Initial setup: #####

README.md

@@ -32,7 +32,7 @@ All updates to this project are documented in our [CHANGELOG](https://github.com
 
 ## Prerequisites
 
-- Java version Oracle JDK 8 or OpenJDK 7
+- Java 8 or 11
 
 ## Install via Maven w/ Gradle