add initial Ledger and capability to open a gnucash file

lib/gnucash.rb

@@ -1,5 +1,8 @@
+require "gnucash/ledger"
 require "gnucash/version"
 
 module Gnucash
-  # Your code goes here...
+  def self.open(fname)
+    Ledger.new(fname)
+  end
 end

lib/gnucash/ledger.rb

@@ -0,0 +1,10 @@
+require "zlib"
+require "nokogiri"
+
+module Gnucash
+  class Ledger
+    def initialize(fname)
+      @ng = Nokogiri.XML(Zlib::GzipReader.open(fname).read)
+    end
+  end
+end