oraclejdk7 is EoLed as far as I'm concerned

.travis.yml

@@ -5,7 +5,6 @@ install:
 script:
 - "./gradlew -S -i"
 jdk:
-- oraclejdk7
 - oraclejdk8
 - openjdk7
 cache:

build.gradle

@@ -91,7 +91,7 @@ bintray {
      * the JDK7 build. This is to prevent multiple attempts by the build matrix
      * to publish the artifacts
      */
-    dryRun = !((System.env.TRAVIS_TAG as boolean) && (System.env.TRAVIS_JDK_VERSION == 'oraclejdk7'))
+    dryRun = !((System.env.TRAVIS_TAG as boolean) && (System.env.TRAVIS_JDK_VERSION == 'openjdk7'))
 
     pkg {
         userOrg = 'jruby-gradle'

src/main/java/com/github/jrubygradle/jem/GemInstallEvent.java

@@ -0,0 +1,12 @@
+package com.github.jrubygradle.jem;
+
+import java.io.File;
+
+/**
+ * Interface defining the appropriate callback even to hook into the
+ * {@code GemInstaller}
+ */
+public interface GemInstallEvent {
+    public void onSuccess(Gem gem, File installationDir);
+    public void onFailure(Gem gem, File installationDir);
+}