Improve profile header jasmine test

* append html to spec.content() instead of body
* don't append the unused conversations modal fixture
* actually test that showModal has been called

spec/javascripts/app/views/profile_header_view_spec.js

@@ -33,16 +33,16 @@ describe("app.views.ProfileHeader", function() {
 
   describe("showMessageModal", function() {
     beforeEach(function() {
-      $("body").append("<div id='conversationModal'/>").append(spec.readFixture("conversations_modal"));
+      spec.content().append("<div id='conversationModal'/>");
     });
 
     it("calls app.helpers.showModal", function() {
       spyOn(app.helpers, "showModal");
       this.view.showMessageModal();
-      expect(app.helpers.showModal);
+      expect(app.helpers.showModal).toHaveBeenCalled();
     });
 
-    it("app.views.ConversationsForm with correct parameterswhen modal is loaded", function() {
+    it("initializes app.views.ConversationsForm with correct parameters when modal is loaded", function() {
       gon.conversationPrefill = [
         {id: 1, name: "diaspora user", handle: "diaspora-user@pod.tld"},
         {id: 2, name: "other diaspora user", handle: "other-diaspora-user@pod.tld"},