add simple unified diff viewer

# Conflicts:
#	.eslintrc

node_modules/ace/lib/ace/line_widgets.js

@@ -214,7 +214,7 @@ function LineWidgets(session) {
         if (!w.coverGutter) {
             w.el.style.zIndex = 3;
         }
-        if (!w.pixelHeight) {
+        if (w.pixelHeight == null) {
             w.pixelHeight = w.el.offsetHeight;
         }
         if (w.rowCount == null) {

node_modules/ace/lib/ace/mode/diff.js

@@ -38,7 +38,7 @@ var FoldMode = require("./folding/diff").FoldMode;
 
 var Mode = function() {
     this.HighlightRules = HighlightRules;
-    this.foldingRules = new FoldMode(["diff", "index", "\\+{3}", "@@|\\*{5}"], "i");
+    this.foldingRules = new FoldMode(["diff", "@@|\\*{5}"], "i");
 };
 oop.inherits(Mode, TextMode);
 

package.json

@@ -109,7 +109,7 @@
         "c9.ide.run.build": "#0598fff697",
         "c9.ide.run.debug.xdebug": "#9956689819",
         "c9.ide.save": "#4cda35bfdb",
-        "c9.ide.scm": "#2af39fcbb5",
+        "c9.ide.scm": "#b7bce1f37f",
         "c9.ide.terminal.monitor": "#1a4092ede2",
         "c9.ide.test": "#102942ae4e",
         "c9.ide.test.mocha": "#fc053b23d2",