Fix tense

Author: tangjm

1-js/13-modules/01-modules-intro/article.md

@@ -13,7 +13,7 @@ To name some (for historical reasons):
 - [CommonJS](http://wiki.commonjs.org/wiki/Modules/1.1) -- the module system created for Node.js server.
 - [UMD](https://github.com/umdjs/umd) -- one more module system, suggested as a universal one, compatible with AMD and CommonJS.
 
-Now all these slowly become a part of history, but we still can find them in old scripts.
+Now these all slowly became a part of history, but we still can find them in old scripts.
 
 The language-level module system appeared in the standard in 2015, gradually evolved since then, and is now supported by all major browsers and in Node.js. So we'll study the modern JavaScript modules from now on.