fix: save npx to dev

.circleci/config.yml

@@ -60,7 +60,7 @@ jobs:
       # they recommend using npx to install node 8 and then use it to run semantic-release (https://github.com/semantic-release/semantic-release/blob/caribou/docs/support/node-version.md)
       # since node 7.10 comes with npm 4 and npx is only available on npm >= 5 it has to be installed first, and run from the local node_modules
       # TODO: we should replace the following line with just "npm run semantic-release" once there's a node:8 image available at circle-ci
-      - run: npm install npx && node_modules/npx/index.js -p node@8 -c "npx semantic-release"
+      - run: npm install --save-dev npx && node_modules/npx/index.js -p node@8 -c "npx semantic-release"
 
 workflows:
   version: 2