fix the link to coding convention.

Valentin Stoychev · Valentin Stoychev · commit 63746df3dd83 · 2016-05-20T16:14:15.000+03:00
diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
@@ -148,4 +148,4 @@ All code contributed to this project should adhere to a consistent style, so ple
 - Declare variables at the top of a scope
 - Return early
 
-For a more detailed guide, check the [Coding Convention](CodingConvention.md). 
+For a more detailed guide, check the [Coding Convention](https://github.com/NativeScript/NativeScript/blob/master/CodingConvention.md). 
