Allow missing GPG env vars when running on a fork (twilio#491)

.travis.yml

@@ -1,10 +1,9 @@
 language: java
 sudo: false
-## export GPG details
 before_install:
   - wget https://github.com/sormuras/bach/raw/master/install-jdk.sh
-  - echo $GPG_SECRET_KEYS | base64 --decode | $GPG_EXECUTABLE --import
-  - echo $GPG_OWNERTRUST | base64 --decode | $GPG_EXECUTABLE --import-ownertrust
+  - echo $GPG_SECRET_KEYS | base64 --decode | $GPG_EXECUTABLE --import || true
+  - echo $GPG_OWNERTRUST | base64 --decode | $GPG_EXECUTABLE --import-ownertrust || true
 matrix:
   include:
 # OpenJDK
@@ -39,7 +38,7 @@ notifications:
       - secure: MkRPjhMDkLMT0tKhSzSAEEdLxKlFrcEw00FBgpcpIl50kSpe3gxCJsm2bz5+LySblCfY1nI5D1+R++eB5cxJzgZvEBWIXQnGJVAV+X7WW1CI1FBZlv6FNLBe5gVPPzo5kIIM1g3o7AaERcraHK9h9S9N8cpnBRHe+Xf6wTRqmwo=
       - secure: iRd6XcgHGFSJ/eS1ZwCUgUVTK0a+JAPmyPEx/OdFbma6DvF8WBhWtW5Q1dyrjQ3JWU8DW2Att9jRnGHd9F5wWWcykxYbD9DXrlfqCZpec9pHzEMAud9MG1PqK0d3y2oyjwps/fQ092PJcn9/y7zX6tzdVWKaKUe4iRDs1u1ehUo=
 install:
-    - mvn --settings .maven.xml install -DskipTests=true -Dgpg.skip -Dmaven.javadoc.skip=true -B -V
+  - mvn --settings .maven.xml install -DskipTests=true -Dgpg.skip -Dmaven.javadoc.skip=true -B -V
 deploy:
   - provider: script
     script: make docker-build && make docker-push
@@ -52,4 +51,4 @@ deploy:
     skip_cleanup: true
     on:
       tags: true
-      jdk: openjdk8
+      jdk: openjdk8