title: tavis ci, jekyll, gh-pages: can't seem to push to gh-pages branch
body: <p>I'm trying to use Travis CI to build my Jekyll site and push to my gh-pages branch on Github. It's not working, I probably don't know what I'm doing.</p>
  
  <p>The error is:<br>
  <code>error: src refspec gh-pages does not match any.</code><br>
  <code>error: failed to push some refs to 'https://github.com/jshwlkr/jshwlkr.info.git'</code></p>
  
  <p>.travis.yml here: <a href="https://github.com/jshwlkr/jshwlkr.info/edit/master/.travis.yml" rel="nofollow noreferrer">https://github.com/jshwlkr/jshwlkr.info/edit/master/.travis.yml</a></p>
  
  <pre><code>branches:
    only:
    - master
  language: node_js
  node_js:
  - '6'
  before_install:
  - rvm install 2.2.3
  - curl -o- -L https://yarnpkg.com/install.sh | bash
  before_script:
  - gem install bundler
  - bundle install
  - mkdir _site
  - git clone https://$GITHUB_TOKEN@github.com/jshwlkr/jshwlkr.info.git -v --branch gh-pages _site
  - git status
  
  after_success:
  - cd _site
  - git config user.email "email.me@jshwlkr.info"
  - git config user.name "jshwlkr"
  - git add --all
  - git status
  - git commit -a -m "Travis #$TRAVIS_BUILD_NUMBER"
  - git push --force origin gh-pages
  - bundle exec rake webmention
  </code></pre>
  
  <p>last build here: <a href="https://travis-ci.org/jshwlkr/jshwlkr.info/builds/268142486" rel="nofollow noreferrer">https://travis-ci.org/jshwlkr/jshwlkr.info/builds/268142486</a></p>
  
  <p>(I'm eventually going to either push to an additional server, or rsync. That's what those comments are.)</p>