Add CI "HOMEPAGE" variable to package.json before building

.gitlab-ci.yml

@@ -2,7 +2,10 @@ image: node:6.5.0
 
 build:
   stage: build
+  variables:
+    HOMEPAGE: "https://whatsopen.gmu.edu/beta/"
   script:
+  - node -e "require('fs').writeFileSync('./package.json', JSON.stringify(Object.assign(require('./package.json'), {'homepage': process.env.HOMEPAGE}), null, 2));"
   - npm install
   - CI=false npm run build
   artifacts: