chore(travis): ensure BUILD_LEADER_ID is fixed to job number

BUILD_LEADER_ID is needed for semantic-release to pick the right job that
semantic-release publishes under. The default behavior for semantic-release
is to elect a build using the latest node version (which in our case is job
9). This var fixes the job to job 10, which is the actual job we have to
run semantic-release.

.travis.yml

@@ -64,6 +64,7 @@ jobs:
         - if [ "$TRAVIS_PULL_REQUEST" != "false" ] || [ "$TRAVIS_BRANCH" != "master" ]; then echo "the deploy job only runs for the master branch. This build will now exit"; exit 0; fi
         - if [ "$TRAVIS_PULL_REQUEST" == "false" ] && [ "$TRAVIS_BRANCH" == "master" ]; then npm run semantic-release; fi
       env:
+       - BUILD_LEADER_ID=10
        # GH_TOKEN type-detect travis 
        - secure: "MPzfTVm7U1Q/eYhHT3DXwZki5Xn4ODNs/uXEM5PB2m+BxbytaAgU+3JSI0ZREv+JLk9CRnj2yWebaQkm+0ompkPRus0pEFuwEsMJ3HqV4ISj6zWGLPNjeJqy6kGa+m1WlkfHM+Spj7vrmk2yclZsmke4xpeQy9W8nnPDEHe6uoQ="
        # NPM_TOKEN …7f80442b