Minor improvements on commit graph UI (#1380)

* Make "Commit Graph" link a button and translate it

* Add title on Commit Graph page

templates/repo/commits.tmpl

@@ -5,12 +5,12 @@
 	  <div class="ui secondary menu">
 	    {{template "repo/branch_dropdown" .}}
 	    <div class="fitted item">
-	      <div class="ui breadcrumb">
+	      <div class="ui basic small button">
 		<a href="{{.RepoLink}}/graph">
 		  <span class="text">
 		    <i class="octicon octicon-git-branch"></i>
 		  </span>
-		  commit graph
+		  {{.i18n.Tr "repo.commit_graph"}}
 		</a>
 	      </div>
 	    </div>

templates/repo/graph.tmpl

@@ -5,6 +5,7 @@
 
 
 	  <div id="git-graph-container" class="ui segment">
+		  <h1>{{.i18n.Tr "repo.commit_graph"}}</h1>
 	    <div id="rel-container">
 	      <canvas id="graph-canvas">
 		<ul id="graph-raw-list">