Fixing issue #139. Logic in scatter.js for

when yDomain is a constant range (ie, [10,10]) is opposite
of what it should be. Added test cases in lineChartTest and
scatterChartTest.html.

src/models/scatter.js

@@ -107,7 +107,7 @@ nv.models.scatter = function() {
 
       if (y.domain()[0] === y.domain()[1])
         y.domain()[0] ?
-            y.domain([y.domain()[0] + y.domain()[0] * 0.01, y.domain()[1] - y.domain()[1] * 0.01])
+            y.domain([y.domain()[0] - y.domain()[0] * 0.01, y.domain()[1] + y.domain()[1] * 0.01])
           : y.domain([-1,1]);
 
       if ( isNaN(x.domain()[0])) {

test/ScatterChartTest.html

@@ -67,6 +67,14 @@
     Scatter plus line: y=-0.5x + 1.0;
     <svg></svg>
   </div>
+  <div id="test14" class="chart third">
+    Scatter chart: duplicate y values
+    <svg></svg>
+  </div>
+  <div id="test15" class="chart third">
+    Scatter chart: duplicate x values
+    <svg></svg>
+  </div>
 
 
 
@@ -103,6 +111,25 @@ defaultChartTest("test10", randomData(30,2));
 scatterPlusLineTest("test11", randomDataSloped(2,0));
 scatterPlusLineTest("test12", randomDataSloped(2,10));
 scatterPlusLineTest("test13", randomDataSloped(-0.5,1));
+defaultChartTest("test14", [
+{key: "Duplicate Y",
+     values: [
+        {x: 0, y: 10}, {x:1, y:10},{x:2, y:10},{x:3, y:10}
+     ]
+    }
+]);
+
+defaultChartTest("test15",[
+   {key: "Duplicate X",
+      area: true,
+      values: [
+        {x: 4, y: 10},
+        {x: 4, y: 11},
+        {x: 4, y: 12},
+        {x: 4, y: 13}
+      ]
+    }
+]);
 
 function defaultChartTest(container, data, margin) {
   nv.addGraph(function() {

test/lineChartTest.html

@@ -80,6 +80,11 @@
         <svg></svg>
       </div>
 
+      <div class='chart third' id='chart16'>
+        Duplicate Y coordinate points.
+        <svg></svg>
+      </div>
+
       <div class='chart third' id='chart13'>
         Chart in a overflow div with scrolls (new tooltips)
         <svg></svg>
@@ -90,6 +95,7 @@
         <svg></svg>
       </div>
 
+      <div style='clear:both;'></div>
       <div class='chart third' id='chart15'>
         What if there are null, Infinity and NaN values in points?
         <svg></svg>
@@ -155,6 +161,7 @@ defaultChartConfig("chart12", duplicateX(),false);
 defaultChartConfig("chart13",hyperbole(), true, false, {width: 700, height: 400});
 defaultChartConfig("chart14",hyperbole(), false, false, {width: 700, height: 400});
 defaultChartConfig("chart15", withNaNs());
+defaultChartConfig("chart16", duplicateY(), false);
 
 function defaultChartConfig(containerid, data, guideline, useDates, auxOptions) {
   if (auxOptions === undefined) auxOptions = {};
@@ -365,6 +372,16 @@ function duplicateX() {
   ];
 }
 
+function duplicateY() {
+  return [
+    {key: "Duplicate Y",
+     values: [
+        {x: 0, y: 10}, {x:1, y:10},{x:2, y:10},{x:3, y:10}
+     ]
+    }
+  ];
+}
+
 function withNaNs() {
   return [
       {key: "NaN Points",