Fix the docs script when operating with a tag, in Travis

Signed-off-by: Thiago Macieira <thiago.macieira@intel.com>
diff --git a/scripts/update-docs.sh b/scripts/update-docs.sh
index 4b822c7..b35db14 100755
--- a/scripts/update-docs.sh
+++ b/scripts/update-docs.sh
@@ -1,6 +1,6 @@
 #!/bin/sh -ex
-case "$TRAVIS_BRANCH,$TRAVIS_PULL_REQUEST" in
-    dev,false|master,false)
+case "$TRAVIS_BRANCH${TRAVIS_TAG+tag:$TRAVIS_TAG},$TRAVIS_PULL_REQUEST" in
+    dev,false|master,false|tag:*)
         ;;
     *)
         exit 0