Make src/xterm.js ES2015 and export EventEmitter into its own file

Fix #158

test/composition-helper-test.js

@@ -15,7 +15,7 @@ describe('CompositionHelper', function () {
         remove: function () {},
       },
       getBoundingClientRect: function () {
-        return { width: 0 }
+        return { width: 0 };
       },
       style: {
         left: 0,

test/escape_sequences.js

@@ -27,7 +27,7 @@ function pty_write_read(s) {
   return b.toString('utf8', 0, bytes);
 }
 
-// make sure raw pty is at x=0 and has no pending data 
+// make sure raw pty is at x=0 and has no pending data
 function pty_reset() {
     pty_write_read('\r\n');
 }

test/viewport-test.js

@@ -6,6 +6,7 @@ describe('Viewport', function () {
   var viewportElement;
   var charMeasureElement;
   var viewport;
+  var scrollAreaElement;
 
   var CHARACTER_HEIGHT = 10;