Compatibility Serverless 1.x

[Vadorequest]

This plugin doesn't seem compatible with the serverless framework 1.27.3

TypeError: Class extends value undefined is not a function or null
    at new module.exports (/Users/vadorequest/dev/unly.org/node_modules/serverless-slack-plugin/src/index.js:8:47)
    at PluginManager.addPlugin (/Users/vadorequest/dev/unly.org/node_modules/serverless/lib/classes/PluginManager.js:52:28)
    at plugins.forEach.error (/Users/vadorequest/dev/unly.org/node_modules/serverless/lib/classes/PluginManager.js:92:14)
    at Array.forEach (native)
    at PluginManager.loadPlugins (/Users/vadorequest/dev/unly.org/node_modules/serverless/lib/classes/PluginManager.js:88:13)
    at PluginManager.loadServicePlugins (/Users/vadorequest/dev/unly.org/node_modules/serverless/lib/classes/PluginManager.js:142:10)
    at PluginManager.loadAllPlugins (/Users/vadorequest/dev/unly.org/node_modules/serverless/lib/classes/PluginManager.js:84:10)
    at service.load.then (/Users/vadorequest/dev/unly.org/node_modules/serverless/lib/Serverless.js:67:28)
From previous event:
    at runCallback (timers.js:672:20)
    at tryOnImmediate (timers.js:645:5)
    at processImmediate [as _immediateCallback] (timers.js:617:5)
From previous event:
    at __dirname (/Users/vadorequest/dev/unly.org/node_modules/serverless/bin/serverless:28:46)
    at Object.<anonymous> (/Users/vadorequest/dev/unly.org/node_modules/serverless/bin/serverless:46:4)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:390:7)
    at startup (bootstrap_node.js:150:9)
    at bootstrap_node.js:505:3
 
  Get Support --------------------------------------------
     Docs:          docs.serverless.com
     Bugs:          github.com/serverless/serverless/issues
     Issues:        forum.serverless.com
 
  Your Environment Information -----------------------------
     OS:                     darwin
     Node Version:           6.10.3
     Serverless Version:     1.27.3