feat(ui5-tools): libraries can now control chromedriver version

[vladitasev]

Currently third-party libraries that use UI5 Web Components tools cannot control chromedriver version, which may be problematic whenever Google Chrome isn't automatically updated on their system.

To solve this, we're moving chromedriver to a peer dependency rather than a dev dependency to @ui5/webcomponents-tools. All packages, internal or external, must now specify a suitable for them chromedriver version.

BREAKING CHANGE: If you are a UI5 Web Components third-party library author, you need to add a dev dependency to chromedriver in your project.
For example, if you had:

  "devDependencies": {
    "@ui5/webcomponents-tools": "1.0.0-rc.7"
  }

you should change this to:

  "devDependencies": {
    "@ui5/webcomponents-tools": "1.0.0-rc.7",
    "chromedriver": "latest"
  }

Feel free to choose a version that suits your specific use case best, or latest if in doubt.

closes: #1682

[vladitasev]

Note: unfortunately we cannot set a predefined version in .travis.yml as it only allows for stable and beta. This is intended so it's up to us to fix the build on demand whenever a new Google Chrome version arrives.