Use wkhtmltopdf-binary gem instead of bundled binary

Gemfile

@@ -79,6 +79,7 @@ gem 'e_invoice', github: 'internetee/e_invoice', branch: :master
 gem 'lhv', github: 'internetee/lhv', tag: 'v0.1.0'
 gem 'domain_name'
 gem 'haml'
+gem 'wkhtmltopdf-binary'
 
 group :development do
   # deploy

Gemfile.lock

@@ -412,6 +412,7 @@ GEM
       hashdiff (>= 0.4.0, < 2.0.0)
     whenever (0.9.4)
       chronic (>= 0.6.3)
+    wkhtmltopdf-binary (0.12.4)
     xpath (3.2.0)
       nokogiri (~> 1.8)
 
@@ -475,6 +476,7 @@ DEPENDENCIES
   validates_email_format_of (= 1.6.3)
   webmock
   whenever (= 0.9.4)
+  wkhtmltopdf-binary
 
 BUNDLED WITH
    1.17.3

config/initializers/pdfkit.rb

@@ -1,9 +1,4 @@
 PDFKit.configure do |config|
-  installed = %x(which wkhtmltopdf).chomp
-  if installed == "" then
-    installed = "#{Rails.root}/vendor/bin/wkhtmltopdf"
-  end
-  config.wkhtmltopdf = installed
   config.default_options = {
     page_size: 'A4',
     quiet: true,