Make `update_site_branch.sh` remove `.travis.yml`

Instead of using:

  branches:
    except:
      - branch-name

in `.travis.yml`, and keeping the `.travis.yml` file, users
should just add `[skip ci]` to the specified commit message.

Ref: http://docs.travis-ci.com/user/how-to-skip-a-build/
Update `CHANGELOG.md`
v0.3.0