Tweak signin / signup pages.

* Link to the signup page on the signin page.
* Clarify that emails are optional on the signup page.

app/views/sessions/new.html.erb

@@ -18,6 +18,10 @@
           <label for="remember" id="remember-label">Remember</label>
         </div>
 
+        <p class="hint">
+          New to <%= Danbooru.config.app_name %>? <%= link_to "Create a new account", new_user_path %>.
+        </p>
+
         <div class="input">
           <%= submit_tag "Submit", :data => { :disable_with => "Signing in..." } %>
         </div>

app/views/users/new.html.erb

@@ -2,7 +2,7 @@
   <div id="a-new">
     <h1>Sign Up</h1>
 
-    <p>A basic account is <strong>free</strong> and lets you keep favorites, upload artwork, and write comments. If you want <%= link_to "more features", new_user_upgrade_path %> you can upgrade your account later.</p>
+    <p>A basic account is <strong>free</strong> and lets you keep favorites, upload artwork, edit tags, and post comments. If you want <%= link_to "more features", new_user_upgrade_path %> you can upgrade your account later.</p>
 
     <h1 style="margin-bottom: 1em;">This site is open to web crawlers so whatever name you choose will be public!</h1>
 
@@ -10,8 +10,8 @@
 
     <div id="p3">
       <%= simple_form_for(@user, html: {id: "signup-form"}) do |f| %>
-        <%= f.input :name, :as => :string %>
-        <%= f.input :email, :required => false, :as => :email %>
+        <%= f.input :name, as: :string %>
+        <%= f.input :email, required: false, as: :email, hint: "Optional" %>
         <%= f.input :password %>
         <%= f.input :password_confirmation %>