cut redundant builds from the travis config, fixed jenkins script

scripts/jenkins.sh

@@ -1,10 +1,15 @@
 #!/usr/bin/env bash
 
-# generate the latest version of the yaml-tests
-./node_modules/.bin/grunt run:generate_yaml_tests --es_branch="=$ES_V"
-
 export VERBOSE="true"
 
+if [ -x $ES_V ]; then
+  echo "missing ES_V environment var"
+  exit 1
+fi
+
+# generate the latest version of the yaml-tests
+node scripts/generate --es_branch="=$ES_V" --no-api
+
 # unit tests
 ./node_modules/.bin/mocha test/unit/test_*.js \
   --require should \