travis: specify node v6.10

.nvmrc

-6.10
\ No newline at end of file

.travis.yml

@@ -9,7 +9,7 @@ python:
 install:
   - pip install cookiecutter
   - pip install invoke==0.14.0
-  - nvm install node
-  - nvm use node
+  - nvm install 6.10
+  - nvm use 6.10
 script:
   - invoke test

{{cookiecutter.app_name}}/webpack.config.js

@@ -33,7 +33,7 @@ module.exports = {
   resolve: {
     extensions: ['.js', '.jsx', '.css']
   },
-  devtool: debug ? '#inline-sourcemap' : null,
+  devtool: debug ? '#inline-sourcemap' : false,
   devServer: {
     headers: { 'Access-Control-Allow-Origin': '*' }
   },