open both plain text and gzipped gnucash files

lib/gnucash/book.rb

@@ -9,7 +9,11 @@ module Gnucash
     attr_accessor :end_date
 
     def initialize(fname)
-      @ng = Nokogiri.XML(Zlib::GzipReader.open(fname).read)
+      begin
+        @ng = Nokogiri.XML(Zlib::GzipReader.open(fname).read)
+      rescue Zlib::GzipFile::Error
+        @ng = Nokogiri.XML(File.read(fname))
+      end
       book_nodes = @ng.xpath('/gnc-v2/gnc:book')
       if book_nodes.count != 1
         raise "Error: Expected to find one gnc:book entry"

spec/gnucash_spec.rb

@@ -1,3 +1,12 @@
 describe Gnucash do
-
+  describe '.open' do
+    it 'opens a gzipped gnucash book' do
+      book = Gnucash.open("spec/books/sample.gnucash")
+      book.is_a?(Gnucash::Book).should be_true
+    end
+    it 'opens a plain text gnucash book' do
+      book = Gnucash.open("spec/books/sample-text.gnucash")
+      book.is_a?(Gnucash::Book).should be_true
+    end
+  end
 end