refactored IS NOT NULL logic to be more efficient

lib/utils.js

@@ -297,8 +297,7 @@ var Utils = module.exports = {
     case 'eq':
       return '='
     case 'ne':
-      if (val) return '!='
-      else return 'IS NOT'
+      return val ? '!=' : 'IS NOT'
     case 'between':
     case '..':
       return 'BETWEEN'