Switch from homepage to repository in pubspec (#687)

Author: devoncarew

pubspec.yaml

@@ -1,7 +1,7 @@
 name: http
 version: 0.13.5-dev
-homepage: https://github.com/dart-lang/http
 description: A composable, multi-platform, Future-based API for HTTP requests.
+repository: https://github.com/dart-lang/http
 
 environment:
   sdk: '>=2.14.0 <3.0.0'