update usage of yarn

ts/npmci.install.ts

@@ -1,7 +1,10 @@
 import * as plugins from './npmci.plugins'
 import * as configModule from './npmci.config'
-import { bash, bashNoError } from './npmci.bash'
-import { nvmAvailable } from './npmci.bash'
+import {
+  bash,
+  bashNoError,
+  nvmAvailable,
+  yarnAvailable } from './npmci.bash'
 
 /**
  * Install a specific version of node
@@ -28,7 +31,7 @@ export let install = async (versionArg) => {
   await bash('node -v')
   await bash('npm -v')
   // lets look for further config
-  configModule.getConfig()
+  await configModule.getConfig()
     .then(async configArg => {
       plugins.beautylog.log('Now checking for needed global npm tools...')
       for (let npmTool of configArg.globalNpmTools) {
@@ -39,7 +42,11 @@ export let install = async (versionArg) => {
           plugins.beautylog.log(`Tool ${npmTool} is available`)
         } else {
           plugins.beautylog.info(`globally installing ${npmTool} from npm`)
-          await bash(`npm install ${npmTool} -q -g`)
+          if (await yarnAvailable) {
+            await bash(`yarn global add ${npmTool}`)
+          } else {
+            await bash(`npm install ${npmTool} -q -g`)
+          }
         }
       }
       plugins.beautylog.success('all global npm tools specified in npmextra.json are now available!')