issue#89 resolve warning in lib/ferrum/browser/process.rb

'instance variable @user_data_dir not initialized'

Author: Mifrill

lib/ferrum/browser/process.rb

@@ -64,6 +64,7 @@ def initialize(options)
           return
         end
 
+        @user_data_dir = nil
         @logger = options[:logger]
         @process_timeout = options.fetch(:process_timeout, PROCESS_TIMEOUT)