Alchem._urlCheck not recognizing certain URLs

So, `Alchemy._urlCheck` was failing for URLs with special characters in the, such as "~". Some RSS feeds I was working with were giving me problems with this, as node-alchemy would decide my URL was a Text API call, so I adjusted the `Alchemy._urlCheck` logic to use Node's `url` module to detect if a hostname and protocol could be found. I also throw out any URL that contains spaces, which helps with test cases like the one included on line 23 of `test/index.js`.