Add code owners to restrict access. (#1030)

diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
new file mode 100644
index 0000000..184c724
--- /dev/null
+++ b/.github/CODEOWNERS
@@ -0,0 +1,6 @@
+# Code owners file.
+# This file controls who is tagged for review for any given pull request.
+
+# For anything not explicitly taken by someone else:
+*               @census-instrumentation/global-owners @rakyll @rghetia 
+