GitLab

* add codecov.io service.
Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* update
Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* only PR or master branch (for coverage badge)
Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* update
Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* update init
Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>