Added initial code to composite.js.

Also required it in index.js. Basic composition working.

index.js

@@ -116,6 +116,7 @@ require("./lib/drawing")(gm.prototype);
 require("./lib/convenience")(gm.prototype);
 require("./lib/command")(gm.prototype);
 require("./lib/compare")(gm.prototype);
+require("./lib/composite")(gm.prototype);
 
 /**
  * Expose.

lib/composite.js

@@ -17,3 +17,11 @@ var utils = require('./utils');
  * @param {String} [mask] Path to the image with opacity informtion. Grayscale.
  */
 
+module.exports = exports = function(proto) {
+    proto.composite = function(other, mask) {
+        this.in(other);
+        this.subCommand("composite");
+
+        return this;
+    }
+}