Add unittest

Add unittest

[   13s] + ./seahash
[   13s]
[   13s] running 15 tests
[   13s] test buffer::tests::not_equal ... ok
[   13s] test buffer::tests::pop ... ok
[   13s] test buffer::tests::push ... ok
[   13s] test buffer::tests::position_depedent ... ok
[   13s] test buffer::tests::seq ... ok
[   13s] test buffer::tests::shakespear ... ok
[   13s] test buffer::tests::zero_senitive ... ok
[   13s] test helper::tests::diffuse_test_vectors ... ok
[   13s] test helper::tests::read_int_ ... ok
[   13s] test helper::tests::read_u64_ ... ok
[   13s] test stream::tests::match_optimized ... ok
[   13s] test impl_std::tests::hash_write_trait ... ok
[   13s] test stream::tests::chunked_equiv ... ok
[   13s] test reference::tests::shakespear ... ok
[   13s] test buffer::tests::zero ... ok
[   13s]
[   13s] test result: ok. 15 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.17s