use icon instead of help button

Netdisco/views/ajax/device/netmap.tt

@@ -1,25 +1,10 @@
-<div id="netmaphelp">
-<button
-  class="btn btn-small btn-info" rel="popover"
-  data-title="Neighbor Map Controls"
-  data-html="true"
-  data-content="
-    <ul>
-      <li>Click and drag to pan</li>
-      <li>Mouse-wheel scroll to zoom</li>
-      <li>Hover to hightlight neighbors</li>
-      <li>Click to view device's map</li>
-    </ul>"
-  data-placement='top' data-trigger='click'>
-    Help
-</button>
-</div>
-
 <script>
 
+// show our help icon
+d3.select('#netmap_help_img').style('display', 'inline');
+
 var winHeight = window.innerHeight;
 var winWidth  = window.innerWidth;
-var helpHeight = document.getElementById("netmaphelp").getBoundingClientRect().height;
 
 var tree = d3.layout.tree()
     .size([360, winHeight])
@@ -38,9 +23,9 @@ var loc = {};
 var neighbors_data = {};
 
 // main SVG background, with support for pan/zoom
-var svg = d3.select("#netmap_pane").insert("svg", "#netmaphelp")
+var svg = d3.select("#netmap_pane").append("svg")
     .attr("width", winWidth - 50)
-    .attr("height", winHeight - (100 + helpHeight))
+    .attr("height", winHeight - 100)
     .attr("pointer-events", "all")
   .append('g')
     .call(d3.behavior.zoom().on("zoom", redraw))