ES6-style constructor added to documentation

doc/classes.texi

@@ -323,17 +323,22 @@ class is causing the issue.
 
 @node Constructors
 @subsection Constructors
-In JavaScript, we are used to functions themselves being a constructor
+A ``constructor'' in JavaScript is simply a function---whether or not
-because only constructors can be instantiated. With ease.js, constructors
+it actually constructs a new object depends on whether the @code{tt}
-are handled in a manner similar to most other languages, by providing a
+keyword is used.  With ease.js, constructors are handled in a manner
-separate method. The implementation ease.js chose is very similar to that of
+similar to most other languages: by providing a separate method.
-PHP's (@pxref{Constructor Implementation}).
+
+Until the release of ECMAScript@tie{}6, which introduced the @code{class}
+keyword, there was no convention for constructors defined in this
+manner.  The implementation ease.js chose is very similar to that of
+PHP's (@pxref{Constructor Implementation}):
 
 @float Figure, f:constructor
 @verbatim
     var Foo = Class( 'Foo',
     {
-        'public __construct': function( name )
+        // may also use `construct`; see below
+        __construct: function( name )
         {
             console.log( 'Hello, ' + name + '!' );
         }
@@ -348,6 +353,31 @@ PHP's (@pxref{Constructor Implementation}).
 @caption{Declaring constructors using ease.js}
 @end float
 
+ease.js introduced the @code{constructor} method in version@tie{}0.2.7
+to match the ES6 ``class'' implementation; it is an alias for
+@code{__construct}.  This method name may be used prior to ES6.
+
+@float Figure, f:constructor-es6
+@verbatim
+    // ECMAScript 6 syntax
+    let Foo = Class( 'Foo',
+    {
+        // you may still use __construct
+        constructor( name )
+        {
+            console.log( 'Hello, ' + name + '!' );
+        }
+    } );
+
+    // instantiate the class, invoking the constructor
+    Foo( 'World' );
+
+    // Output:
+    // Hello, World!
+@end verbatim
+@caption{Declaring constructors in an ECMAScript 6 style}
+@end float
+
 When the class is instantiated, the constructor is invoked, permitting you
 do to any necessary initialization tasks before the class can be used. The
 constructor operates exactly how you would expect a constructor to in