Merge pull request #1451 from SergeAstapov/patch-1

Update `git clone` command in README.md under contribution

Author: NullVoxPopuli

README.md

@@ -57,7 +57,7 @@ Contributing
 
 ### Installation
 
-* `git clone <repository-url>`
+* `git clone https://github.com/emberjs/ember-test-helpers.git`
 * `cd ember-test-helpers`
 * `yarn install`