fix 404 at README.md (docker#519)

Fixes docker#518

Signed-off-by: kurochan <[email protected]>

Author: kurochan

README.md

@@ -32,7 +32,7 @@ help. If a reviewer realizes you have based your work on the wrong branch, we'll
 let you know so that you can rebase it.
 
 >**Note**: To contribute code to Docker projects, see the
-[Contribution guidelines](opensource/project/who-written-for).
+[Contribution guidelines](https://docs.docker.com/opensource/project/who-written-for/).
 
 ### Files not edited here
 
@@ -124,7 +124,7 @@ You have three options:
     ```
 
     If you haven't got Docker Compose installed,
-    [follow these installation instructions](/compose/install/).
+    [follow these installation instructions](https://docs.docker.com/compose/install/).
 
     The container runs in the background and incrementally rebuilds the site each
     time a file changes. You can keep your browser open to http://localhost:4000/
@@ -167,7 +167,7 @@ directly on docs.docker.com.
 ## Style guide
 
 If you have questions about how to write for Docker's documentation, please see
-the [style guide](/opensource/doc-style/). The style guide provides
+the [style guide](https://docs.docker.com/opensource/doc-style/). The style guide provides
 guidance about grammar, syntax, formatting, styling, language, or tone. If
 something isn't clear in the guide, please submit an issue to let us know or
 submit a pull request to help us improve it.