fix style in message threads

app/views/mailbox/message_threads/_form.haml

@@ -1,8 +1,10 @@
 = form_for @message_thread, url: mailbox_message_threads_path, method: :post do |f|
-  %label
-    recipients: 
-  = f.text_field :recipients, multiple: true, required: true
-  %label
-    Subject: 
-  = f.text_field :subject
+  .form-group
+    %label
+      recipients: 
+    = f.text_field :recipients, multiple: true, required: true, class: 'form-control'
+  .form-group
+    %label
+      Subject: 
+    = f.text_field :subject, class: 'form-control'
   = render partial: 'messages/form', locals: { f: f }

app/views/messages/_form.haml

@@ -1,3 +1,5 @@
-= f.fields_for Message.new do |message_form|
-  = message_form.rich_text_area :content
-= f.submit
+.my-3
+  = f.fields_for Message.new do |message_form|
+    = message_form.rich_text_area :content
+  .my-3
+    = f.submit "Send", class: 'btn btn-primary'