change travis builds to publish docker images with tag 'nightly' (#71)

diff --git a/.travis.yml b/.travis.yml
index 6366af6..43abe1b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -46,7 +46,7 @@
       condition: "${TRAVIS_TAG%@*} = dockerskeleton || ${TRAVIS_TAG%@*} = example"
       repo: apache/incubator-openwhisk-runtime-docker
   - provider: script
-    script: "./tools/travis/publish.sh openwhisk dockerskeleton latest && ./tools/travis/publish.sh openwhisk example latest"
+    script: "./tools/travis/publish.sh openwhisk dockerskeleton nightly && ./tools/travis/publish.sh openwhisk example nightly"
     on:
       branch: master
       repo: apache/incubator-openwhisk-runtime-docker
diff --git a/tools/travis/publish.sh b/tools/travis/publish.sh
index 23bae25..a10502e 100755
--- a/tools/travis/publish.sh
+++ b/tools/travis/publish.sh
@@ -48,8 +48,8 @@
   -PdockerImagePrefix=${IMAGE_PREFIX} \
   -PdockerImageTag=${IMAGE_TAG}
 
-    # if doing latest also push a tag with the hash commit
-  if [ ${IMAGE_TAG} == "latest" ]; then
+    # if doing nightly also push a tag with the hash commit
+  if [ ${IMAGE_TAG} == "nightly" ]; then
     SHORT_COMMIT=`git rev-parse --short HEAD`
     TERM=dumb ./gradlew \
     ${GRADLE_BUILD} \