Update twitter widget and username

Author: kynan

_config.yml

@@ -5,7 +5,7 @@ description: > # this means to ignore newlines until "baseurl:"
   Python Sprints is a website to promote sprints in the Python community
 baseurl: "" # the subpath of your site, e.g. /blog/
 url: "https://python-sprints.github.io/" # the base hostname & protocol for your site
-twitter_username: py_sprints
+twitter_username: PythonSprints
 github_username:  python-sprints
 
 # Build settings

_config_dev.yml

@@ -5,7 +5,7 @@ description: > # this means to ignore newlines until "baseurl:"
   Python Sprints is a website to promote sprints in the Python community
 baseurl: "" # the subpath of your site, e.g. /blog/
 url: "http://localhost:4000"
-twitter_username: py_sprints
+twitter_username: PythonSprints
 github_username:  python-sprints
 
 # Build settings

_includes/footer.html

@@ -2,11 +2,11 @@
     <div class="row container-fluid">
         <div class="footer__twitter-container col-md-5 text-center">
             <a class="twitter-timeline"
-               data-width="400"
+               data-width="600"
                data-height="400"
                data-theme="light"
                data-link-color="#2B7BB9"
-               href="https://twitter.com/PythonSprints">Tweets by @PythonSprints</a>
+               href="https://twitter.com/{{ site.twitter_username }}">Tweets by {{ site.twitter_username }}</a>
             <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
         </div>
         <div class="col-md-7">