Refactor url generation

[dkubb]

This branch refactors the URL generation to use URI to construct the string, rather than using string concatenation directly.

It also cleans up a few small build issues I encountered while working with the gem in development.

[pat]

Certainly feels cleaner. Would be great to see this merged in.

[bartt]

Splitting URL strings on characters is never a good idea. Use URI instead.

[dkubb]

It's not splitting a URL, it's splitting a hostname that is a host with an optional port. afaik there is no URI method to parse/split hostname. To use URI you'd have to use string concatenation to build a URL string first then split it using something like URI.split, which kind of defeats the purpose of this change and is (IMHO) worse than splitting a "host with port" in the way this code does now.

If I'm wrong and there is a URI method that you can hand a hostname to, let please me know and I'll update the PR.