Bump webpacker from 3.2.1 to 3.4.1 (#70)

Bumps [webpacker](https://github.com/rails/webpacker) from 3.2.1 to 3.4.1.
- [Release notes](https://github.com/rails/webpacker/releases)
- [Changelog](https://github.com/rails/webpacker/blob/master/CHANGELOG.md)
- [Commits](rails/webpacker@v3.2.1...v3.4.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Gemfile

@@ -9,7 +9,7 @@ gem 'rails', '~> 5.1.6'
 gem 'pg', '= 0.21.0'
 gem 'puma', '~> 3.11'
 gem 'sass-rails', '~> 5.0'
-gem 'webpacker', '~> 3.2'
+gem 'webpacker', '~> 3.4'
 gem 'uglifier', '>= 1.3.0'
 gem 'coffee-rails', '~> 4.2'
 gem 'turbolinks', '~> 5'

Gemfile.lock

@@ -124,7 +124,7 @@ GEM
     public_suffix (3.0.2)
     puma (3.11.3)
     rack (2.0.4)
-    rack-proxy (0.6.3)
+    rack-proxy (0.6.4)
       rack
     rack-test (1.0.0)
       rack (>= 1.0, < 3)
@@ -217,7 +217,7 @@ GEM
       activemodel (>= 5.0)
       bindex (>= 0.4.0)
       railties (>= 5.0)
-    webpacker (3.2.1)
+    webpacker (3.4.1)
       activesupport (>= 4.2)
       rack-proxy (>= 0.6.1)
       railties (>= 4.2)
@@ -256,7 +256,7 @@ DEPENDENCIES
   tzinfo-data
   uglifier (>= 1.3.0)
   web-console (>= 3.3.0)
-  webpacker (~> 3.2)
+  webpacker (~> 3.4)
 
 BUNDLED WITH
    1.15.1