fix: example in the readme and other minor changes

[mxschmitt]

Changes:

• Use -D in NPM install
• Fix example by using the class selector instead of the element selector (timeout before)
• Add example for overwriting the launch and context options
• Add support for overwriting context options
• Fix test-runner by adding commander dependency. Previously it lead to commander not found require error. (not reproducible upstream since we have the package installed there)
• Feat instead of the need to pass a directory we use . as a default one now. Like Jest is doing.
• Bump dependencies -> fixes deprecation warning of 5 packages.

Fixes #61 Fixes #60