Максимов - Лабораторная работа #2

Code and decode tests must be independent. I mean write 2 tests like example (for Code method):
```
// Arrange
std::string source = "Hello!";
std::string expectedResult = "00100111";    // It's random combination and it isn't correct
HuffmanAlgorithm huff;

// Act
std::string result = huff.Code(source);

// Assert

EXPECT_EQ(expectedResult, result);
```