Before you begin, we much install the SpecFlow Utility Extension.
Tools > Install and Extensions - Online : Search, "SpecFlow for . . ." (It would list the version of IDE you are using)
Once installed, close and reopen your visual studio. If done properly, when you add a new file to the project, you should
see new items to choose from that are specific to Specflow.
About SpecFlow & XProj
Currently (01/01/2017) - If you were to create an XProj Project and attempt to add a Feature/Hook/Definition File, you will
notice that you will not be able to. The Solution, close your project, create a new Solution and add a CSProj project. From that
you will be able to create a Feature/Hook/Definition file, you just need the file made. Open the folder in File Explorer that
contains the newly created Feature/Hook/Definition and copy the file. Open your Xproj and Paste it where you want it to reside.