+ support 'filter' prop in imageTransform

Author: RubaXa

lib/FileAPI.Image.js

@@ -356,6 +356,7 @@
 , type: params.type || file.type || 'image/png'
 , quality: params.quality || 1
 , overlay: params.overlay
+, filter: params.filter
 });
 
 queue.inc();

lib/FileAPI.core.js

@@ -1523,7 +1523,7 @@
 var key;
 for( key in trans ){
 if( trans.hasOwnProperty(key) ){
-if( !(trans[key] instanceof Object || key === 'overlay') ){
+if( !(trans[key] instanceof Object || key === 'overlay' || key === 'filter') ){
 returntrue;
 }
 }