Improves robustness and small refactor

I discovered an error in the current url scheme regex
````regex
[http|https]+
````

Gets alot of false positives e.g.
http://rubular.com/r/QbD4dVJYIg

I added a Regex::URL[:scheme] helper to make the code more DRY

I've added tests to support the changes - it would be an idea to add more regex helpers and test them before testing the final output from embedda.