make codecov bot to comment on PRs

.codecov.yml

@@ -1 +1,7 @@
-comment: false
+comment:
+  layout: "reach, diff, flags, files"
+  behavior: default
+  require_changes: false  # if true: only post the comment if coverage changes
+  require_base: no        # [yes :: must have a base report to post]
+  require_head: yes       # [yes :: must have a head report to post]
+  branches: null          # branch names that can post comment

.travis.yml

@@ -2,7 +2,6 @@ os: linux
 language: go
 go:
   - 1.12.9
-
 env:
   global:
     - GOPROXY=https://proxy.golang.org
@@ -33,10 +32,8 @@ matrix:
       before_install:
         - sudo apt-get install -y libvirt-dev
       script: make test
-
 after_success:
   - bash <(curl -s https://codecov.io/bash)
-
 notifications:
     webhooks: https://www.travisbuddy.com/
     on_success: never # travisbuddy don't comment on successful