- Removed links to the gov uk stylesheets

- Deleted /stylesheets folder
- Removed sass build from gulpfile
- Changed gov links to usa links
- Changed other govuk styles, like breadcrumbs
- Changed name of uk_components file to us_components
- Fixed a few tests that broke on account of the changes

app/templates/withnav_template.html

@@ -18,7 +18,7 @@
       {% if help %}
         <div class="grid-col-8">
       {% else %}
-        <div class="grid-col-9 padding-left-4 sub-content">
+        <div class="grid-col-9 padding-left-4 usa-prose site-prose">
       {% endif %}
         {% block beforeContent %}
           {% block backLink %}{% endblock %}