2.0.0: Allow recursion

It is now possible to spawn child instances from spawned instances, creating a tree-structure with top-down inheritance of enabled status.
Also an error has been fixed which prevented the library to be run under nodeJS, where there is no window object.

• test: do not actually log test output (94548a6)
• style: fix code style (ed31daf)
• feat: Allow recursive spawning (09a01a0)
• test: More prefix tests (5a36d55)
• test: Add basic tests using mocha, chai & sinon (e6f2fa0)
• chore: Fix prettier config (524ac3e)
• fix: Allow running under nodeJS (382fd27)