[Issue #123] Adding link to Git submodule documentation in installation section

README.md

@@ -30,7 +30,7 @@ Of course, AFNetworking remains the premiere networking library available for Ma
 
 _The infrastructure and best practices for distributing Swift libraries is currently in flux... which is to say, the current installation process kinda sucks._
 
-1. Add Alamofire as a submodule by opening the Terminal, `cd`-ing into your top-level project directory, and entering the command `git submodule add https://github.com/Alamofire/Alamofire.git`
+1. Add Alamofire as a [submodule](http://git-scm.com/docs/git-submodule) by opening the Terminal, `cd`-ing into your top-level project directory, and entering the command `git submodule add https://github.com/Alamofire/Alamofire.git`
 2. Open the `Alamofire` folder, and drag `Alamofire.xcodeproj` into the file navigator of your Xcode project.
 3. In Xcode, navigate to the target configuration window by clicking on the blue project icon, and selecting the application target under the "Targets" heading in the sidebar.
 4. In the tab bar at the top of that window, open the "Build Phases" panel.