Use the right code coverage definitions (tendermint#352)

by moving the `codecov.yml` file from .github the root folder.

---

#### PR checklist

- [ ] Tests written/updated
- [ ] Changelog entry added in `.changelog` (we use [unclog](https://github.com/informalsystems/unclog) to manage our changelog)
- [ ] Updated relevant documentation (`docs/` or `spec/`) and code comments

codecov.yml

@@ -2,26 +2,24 @@ coverage:
   precision: 2
   round: down
   range: "70...100"
-  github_checks:
-    annotations: false
-
   status:
     project:
       default:
-        threshold: 1%
-    patch: on
+        threshold: 20%
+    patch: off
     changes: off
 
-comment:
-  layout: "diff, files"
-  behavior: default
-  require_changes: no
-  require_base: no
-  require_head: yes
+github_checks:
+  annotations: false
+
+comment: false
 
 ignore:
   - "docs"
   - "DOCKER"
   - "scripts"
   - "**/*.pb.go"
   - "libs/pubsub/query/query.peg.go"
+  - "*.md"
+  - "*.rst"
+  - "*.yml"