Add TOS/PP links to the /signin page

fixes #255

app/scripts/templates/sign_in.mustache

@@ -32,4 +32,8 @@
     <a href="/reset_password" class="left">{{#t}}Forgot password?{{/t}}</a>
     <a href="/signup" class="right">{{#t}}Create an account{{/t}}</a>
   </div>
+
+  <div class="privacy-links">
+    {{#t}}By proceeding, I agree to the <a id="fxa-tos" href="/tos">Terms of Service</a> and <a id="fxa-pp" href="/pp">Privacy Notice</a> for Sync.{{/t}}
+  </div>
 </section>

app/styles/main.css

@@ -258,6 +258,10 @@ section p {
   visibility: hidden;
 }
 
+.links + .privacy-links {
+  margin: 20px 0 15px 0;
+}
+
 .cannot-create-account-content {
   margin-top: 105px;
 }