Add Rst status image format

Close #192.

assets/scripts/app/templates/status_images.hbs

@@ -27,3 +27,7 @@
   <label>{{t repositories.asciidoc}}:</label>
   <input type="text" class="asciidoc" {{bindAttr value="view.asciidocStatusImage"}}></input>
 </p>
+<p>
+  <label>{{t repositories.rst}}:</label>
+  <input type="text" class="rst" {{bindAttr value="view.rstStatusImage"}}></input>
+</p>

assets/scripts/app/views/status_images.coffee

@@ -51,3 +51,7 @@ Travis.StatusImagesView = Em.View.extend
   asciidocStatusImage: (->
     "image:#{@get('statusImageUrl')}[\"Build Status\", link=\"#{@get('urlRepo')}\"]"
   ).property('statusImageUrl')
+
+  rstStatusImage: (->
+    ".. image:: #{@get('statusImageUrl')}   :target: #{@get('urlRepo')}"
+  ).property('statusImageUrl')