Add CodeCov config file (ZcashFoundation#51)

* Add CodeCov config file

* Consistent indentation

Author: dconnolly

codecov.yml

@@ -0,0 +1,29 @@
+coverage:
+  range: "50...100"
+  status:
+    project:
+      default:
+        informational: true
+    patch:
+      default:
+        informational: true
+
+parsers:
+  gcov:
+    branch_detection:
+      conditional: yes
+      loop: yes
+      method: yes
+      macro: yes
+
+# comment:
+#   layout: "diff"
+#   # if true: only post the comment if coverage changes
+#   require_changes: true
+
+# This turns off the extra comment; the coverage %'s are still
+# reported on the main PR page as check results
+comment: false
+
+github_checks:
+  annotations: false