Port some extra crypto-square tests from C#

Following @kytrinyx's hint https://github.com/exercism/xruby/pull/54#issuecomment-64657873

Here is the C# source for these additional test cases: https://github.com/exercism/xcsharp/blob/24d4e4ee3283267cbbbc80d9fd425bdc8f558b35/crypto-square/CryptoSquareTest.cs

They pass with my own implementation :wink:
http://exercism.io/submissions/692ef3e976c04f0b8d0254d2431362a4