Revert "Revert coverity in travis - takes too long"

This reverts commit 32da2ec9fd.

Signed-off-by: Andrew DeMaria <lostonamountain@gmail.com>

.travis.yml

@@ -7,6 +7,20 @@ script:
 
 matrix:
   include:
+  - name: coverity
+    script:
+      - echo "coverity scan script"
+    install:
+      - echo "coverity scan install"
+    addons:
+      coverity_scan:
+        project:
+          name: "airsonic/airsonic"
+          description: "A Free and Open Source community driven media server"
+        notification_email: "airsonic@tutanota.com"
+        build_command_prepend: mvn clean
+        build_command: mvn clean
+        branch_pattern: master
   - jdk: openjdk8
   - jdk: oraclejdk9
     before_install: