Keep pullRequestNumber on build not on commit

assets/scripts/app/models/build.coffee

@@ -15,6 +15,7 @@ require 'travis/model'
   finishedAt:       DS.attr('string')
   pullRequest:      DS.attr('boolean')
   pullRequestTitle: DS.attr('string')
+  pullRequestNumber: DS.attr('number')
 
   repo:   DS.belongsTo('Travis.Repo')
   commit: DS.belongsTo('Travis.Commit')

assets/scripts/app/templates/builds/show.hbs

@@ -27,7 +27,7 @@
           <dd class="commit"><a {{bindAttr href="urlGithubCommit"}}>{{formatCommit build.commit}}</a></dd>
           {{#if build.pullRequest}}
             <dt>{{t builds.pullRequest}}</dt>
-            <dd class="pull_request"><a {{bindAttr href="build.commit.compareUrl"}}>#{{build.commit.pullRequestNumber}} {{build.pullRequestTitle}}</a></dd>
+            <dd class="pull_request"><a {{bindAttr href="build.commit.compareUrl"}}>#{{build.pullRequestNumber}} {{build.pullRequestTitle}}</a></dd>
           {{else}}
             {{#if commit.compareUrl}}
               <dt>{{t builds.compare}}</dt>