Update dependencies

### Issue type

**I'm submitting a ...** (check one with "x")

* [ ] bug report
* [ ] feature request
* [x] question about the decisions made in the repository

### Issue description

**Current behavior:**

This project uses a lot of dependencies (and devDependencies), and they're pretty outdated. Doing a fresh `npm install`, it reports dozens of vulnerabilities.

**Expected behavior:**

Having the dependencies mostly up-to-date and having no errors or warnings when installing for the first time.
Are there any plans to update the dependencies? And keep them up-to-date in the future?

**Steps to reproduce:**

Do the [installation steps](https://akveo.github.io/nebular/docs/guides/install-based-on-starter-kit) using npm 6.