Replaced function for extension to use it with Angular v6

[marlon360]

Removed the 'path' dependency from NodeJS and replaced it with own function to use this package with Angular v6.

[dougwilson]

The agreement was to replace it with an npm module, not a ball of code I have to maintain.

[dougwilson]

Also, besides replacing this with a module, the tests need to be added that test the module in a Angular/ browser environment. I believe the proposal was to use Karma to do that 👍

[marlon360]

Found a better solution: #53
Your code stays untouched, but a bundler builds the browser version.
The tests also stay the same, but run with karma in a browser (see Travis at node v6).