Start making buttons look like buttons again

This partially addresses some styling issues on #1369. We now have a
macro for auth buttons, which is fine, but it's not flexible enough wrt
styling across the site.

scss/buttons-knobs.scss

@@ -58,16 +58,3 @@ button.join-leave[data-is-member="true"] {
 button.join-leave[data-is-member="false"] {
     @extend .selected;
 }
-
-form.auth-button {
-    display: inline-block;
-    & > button {
-        margin: 0;
-        padding: 0;
-        color: $green;
-        background: none;
-        border: none;
-        font: inherit;
-        font-weight: bold;
-    }
-}

www/on/%platform/%user_name/index.html.spt

@@ -188,17 +188,16 @@ else:
     <h2>{{ user_name|e }} has not joined Gittip.</h2>
 
     {% if platform in website.signin_platforms or not user.ANON %}
-        Is this you?
         {% if user.ANON %}
+            <p>Is this you? We never collect money for you unless you join.</p>
             {% call auth_button(platform.name, 'opt-in', path['user_name']) %}
-                Opt in
+                Join Gittip
             {% endcall %}
-            to Gittip. We never collect money for you until you do.
         {% else %}
+            <p>Is this yours? Connect it to your Gittip account.</p>
             {% call auth_button(platform.name, 'connect', path['user_name']) %}
-                Connect this {{ platform.display_name }} account
+                Connect
             {% endcall %}
-            to your Gittip account.
         {% endif %}
     {% endif %}