Create using-unreleased-features.html.md
Update using-unreleased-features.html.md
Update using-unreleased-features.html.md

Reformatting and clearer instructions with details
Fixing cocoapods typo
Updating placeholder git URLs to real URLs
Correcting Gem name
Including external links

Included links for Gemfile specs, gem git options and my own blog post about using swift with CocoaPods
Adding backticks and empty line
Merge pull request #43 from palewar/patch-1

Instructions to test-drive unreleased code