Fix a broken link in getting-started.md
Fix a broken link in getting-started.md

- had ;// - not ://
- also xunit has moved to GitHub - according to a note on http://xunit.codeplex.com/
jorik041/FluentAutomation,mirabeau-nl/WbTstr.Net,stirno/FluentAutomation,stirno/FluentAutomation,jorik041/FluentAutomation,stirno/FluentAutomation,jorik041/FluentAutomation,mirabeau-nl/WbTstr.Net,tablesmit/FluentAutomation,tablesmit/FluentAutomation,tablesmit/FluentAutomation