…3476)

The main reason for this change is to be able to update Cucumber library as `grunt-cucumberjs` (mavdi/grunt-cucumberjs#110) does not support cucumber@4 and looks pretty abandoned.

Grunt ecosystem is not very active for a while, so we can expect more issues of this sort in the future. Because of this and to keep docs consistent I've also added NPM scripts to run other test types (for now they just proxy to Grunt) and removed Grunt examples from the documentation.

In the next PR I will update `cucumber` and perform some cleanup of the step definitions.

Use `npm` scripts instead of shell commands and Grunt.

This tag was useful long time ago, when most of the tests were run using PhantomJS. For a long time E2E tests use ChromeHeadless as a the main browser and it is not needed to mark tests using Google Chrome to only run locally. Two removed test cases have identical cases above them, which are run in the ChromeHeadless and other two were updated to run in ChromeHeadless instead of Chrome and will be run both in CI as well as locally.

karma-runner/karma-browserstack-launcher#61

- Fix warnings reported by Travis (https://travis-ci.org/github/karma-runner/karma/builds/677410665/config).
- Remove installation of g++-4.8 as it is no longer needed.
- Remove SAUCE_USERNAME variable as it is configured in the Travis UI now.
- Remove fast_finish as it only makes sense when some jobs are allowed to fail (https://docs.travis-ci.com/user/build-matrix/#fast-finishing). Which is not the case.

Assuming that the issue is concurrent jobs attempting to interact with BrowserStack using the same build ID, this solution attempts to solve it by only interacting with BrowserStack in one of the jobs.

Updated build definition:

- runs complete build on the latest Node
- runs simplified build (without commit validation, lint, test:client and test:integration) on earlier versions on Node

It is not very valuable to run omitted test suits multiple times as they supposed to catch issues, which are usually Node-independent: client code fails in some browsers and API breaking changes, which will affect popular Karma plugins.

Fixes #3468

Had to adjust two steps to use regular expressions as Cucumber does not support optional parameters anymore (cucumber/common#360).
Using regular expressions seems to be a known workaround (https://stackoverflow.com/questions/18346348/optional-parameter-in-cucumber).

Fixes #3211

## [5.0.3](v5.0.2...v5.0.3) (2020-04-29)

### Bug Fixes

* **client:** flush resultsBuffer on engine upgrade ([#3212](#3212)) ([e44ca94](e44ca94)), closes [#3211](#3211)