Add (ui-only) Persona button to login modal

app/assets/javascripts/discourse/templates/modal/login.js.handlebars

@@ -16,6 +16,8 @@
     {{#if Discourse.SiteSettings.enable_github_logins}}
       <button class="btn btn-social github" title="{{i18n login.github.title}}" {{action "githubLogin" target="view"}}>{{i18n login.github.title}}</button>
     {{/if}}
+    <br>
+    <button class="btn btn-social persona" title="{{i18n login.persona.title}}" {{action "personaLogin" target="view"}}>{{i18n login.persona.title}}</button>
   </div>
   <h3 style="text-align:center; margin-bottom:10px;">
     {{i18n login.or}}

app/assets/stylesheets/components/buttons.css.scss

@@ -168,6 +168,12 @@
       content: "g";
     }
   }
+  &.persona {
+    background: $persona;
+    &:before {
+      content: "]";
+    }
+  }
 }
 
 // Button Sizes

app/assets/stylesheets/foundation/variables.scss

@@ -124,6 +124,7 @@ $facebook: #3b5998 !default;
 $twitter: #00bced !default;
 $yahoo: #810293 !default;
 $github: #6d6d6d !default;
+$persona: #606060 !default;
 
 // Layout dimensions
 
@@ -174,4 +175,4 @@ $heart: #fa6c8d;
 $attention_bg: #e4f2f8;
 $attention_fg: #1aaae4;
 
-$header-item-highlight: #ecf8f6;
+$header-item-highlight: #ecf8f6;

config/locales/client.en.yml

@@ -251,6 +251,9 @@ en:
       github:
         title: "Log In with Github"
         message: "Authenticating with Github (make sure pop up blockers are not enabled)"
+      persona:
+        title: "Log In with Any Email Address (Mozilla Persona)"
+        message: "Authenticating with Persona (make sure pop up blockers are not enabled)"
 
     composer:
       saving_draft_tip: "saving"