Using the simplifiedAutoLink option does not return the expected GFM behaviour when parsing links without a http prefix.
Previously, `www.google.com` would be parsed into `<a href="www.google.com">www.google.com</a>`.
With this fix, showdown behaves like GFM, and the result is `<a href="http://www.google.com">www.google.com</a>`
Closes#284, closes#285
Github Flavored Markdown detects urls and mails embeded in the text without any extra markup or delimiter.
This commit adds this feature to showdown through an option called "simplifiedAutoLink".
Related to #164