Re-implement the logic for showing the browser-appropriate installer

 * Re-implement logic for showing browser-appropriate installation
   option

 * Tweak the border styles on the proxy link form

h/static/scripts/browser-test.js

 // TODO - Make this a CommonJS module and move it into
 // the site JS?
-if (window.chrome !== undefined) {
-  var elements = document.getElementsByClassName(
-      "unhide-in-chrome");
-  for (var i=0; i<elements.length; i++) {
-    elements[i].classList.remove("hidden");
-  }
-  elements = document.getElementsByClassName(
-      "hide-in-chrome");
-  for (var i=0; i<elements.length; i++) {
-    elements[i].classList.add("hidden");
-  }
+var env = {
+  browserIsChrome: typeof window.chrome !== 'undefined',
+  browserIsOther: typeof window.chrome === 'undefined',
+};
+
+function hypenate(key) {
+  // 'camelCase' -> 'camel-case'
+  return key.replace(/[a-z]+/g, '$&-').toLowerCase().slice(0, -1);
 }
+
+Object.keys(env).forEach(function (key) {
+  var selector = '.js-' + hypenate(key);
+  var elements = document.querySelectorAll(selector);
+  for (var i = 0; i < elements.length; i++) {
+    if (env[key]) {
+      elements[i].classList.remove('is-hidden');
+    } else {
+      elements[i].classList.add('is-hidden');
+    }
+  }
+});

h/static/styles/footer.scss

@@ -8,9 +8,13 @@
 
   .social-media-link {
     display: inline-block;
-    padding-left: 3px;
-    padding-right: 3px;
+    padding-left: 6px;
+    padding-right: 6px;
     font-size: 16px;
     text-decoration: none;
   }
+
+  .social-media-link:not(:hover) {
+    color: $color-gray;
+  }
 }

h/static/styles/home.scss

@@ -100,28 +100,30 @@
     margin-right: 10px;
   }
 
-  $proxy-border: 2px solid $color-alto;
+  $proxy-border: 1px solid $color-alto;
+  $proxy-border-radius: 4px;
 
   .installer__proxy-form {
     display: flex;
   }
 
   .installer__proxy-link-field {
-    border-top-left-radius: 2px;
-    border-bottom-left-radius: 2px;
+    border-top-left-radius: $proxy-border-radius;
+    border-bottom-left-radius: $proxy-border-radius;
     border-left: $proxy-border;
     border-top: $proxy-border;
     border-bottom: $proxy-border;
     border-right: none;
     padding-left: 10px;
+    min-width: 200px;
   }
 
   .installer__proxy-btn {
     font-weight: bold;
     background-color: $color-gallery;
-    border: 2px solid $color-alto;
-    border-top-right-radius: 2px;
-    border-bottom-right-radius: 2px;
+    border: $proxy-border;
+    border-top-right-radius: $proxy-border-radius;
+    border-bottom-right-radius: $proxy-border-radius;
   }
 
   .home__intro-container {