Fix publishing to npm by travis

[ewelinagr]

Current issue when publishing to npm by travis:

NPM API key format changed recently. If your deployment fails, check your API key in ~/.npmrc.

http://docs.travis-ci.com/user/deployment/npm/

~/.npmrc size: 48

> @thehyve/fractalis@1.4.1-hyve prepublishOnly .

> npm run-script build && npm run-script create-es6-export-file

> @thehyve/fractalis@1.4.1-hyve build /home/travis/build/thehyve/Fractal.js

> webpack --config webpack.config.js --mode production

sh: 1: webpack: not found

npm ERR! file sh

npm ERR! code ELIFECYCLE

npm ERR! errno ENOENT

Hopefully installing dev dependencies will fix the issue...