TravisCI builds fails during npm install

Author: czgtest

.travis.yml

@@ -47,7 +47,7 @@ install:
 - npm install -g vsce
 - npm install -g typescript
 - npm install -g gulp
-- npm install
+- npm install -g npm@2
 # https://github.com/travis-ci/travis-ci/issues/8813
 - rm -f ./node_modules/.bin/which