Remove checksum (#11)

Fixes #6

It's not actually enforced or verified and adds no value currently.

Author: marcqualie

Diff for: lib/diffcrypt/encryptor.rb

@@ -51,7 +51,6 @@ def encrypt(contents, original_encrypted_contents = nil)
       YAML.dump(
         'client' => "diffcrypt-#{Diffcrypt::VERSION}",
         'cipher' => CIPHER,
-        'checksum' => Digest::MD5.hexdigest(Marshal.dump(data)),
         'data' => data,
       )
     end

Diff for: test/diffcrypt/encryptor_test.rb

@@ -10,7 +10,7 @@
 class Diffcrypt::EncryptorTest < Minitest::Test
   def test_it_includes_client_info_at_root
     content = "---\nkey: value"
-    expected_pattern = /---\nclient: diffcrypt-#{Diffcrypt::VERSION}\ncipher: #{Diffcrypt::Encryptor::CIPHER}\nchecksum: [a-z0-9]{32}\ndata:\n  key: #{ENCRYPTED_VALUE_PATTERN}\n/
+    expected_pattern = /---\nclient: diffcrypt-#{Diffcrypt::VERSION}\ncipher: #{Diffcrypt::Encryptor::CIPHER}\ndata:\n  key: #{ENCRYPTED_VALUE_PATTERN}\n/
     assert_match expected_pattern, Diffcrypt::Encryptor.new(TEST_KEY).encrypt(content)
   end