Gostcrypto

- First release of **'gostcrypto'**

- Refactoring and code modification in module **gostcipher** to increase the performance of encryption algorithm 'kuznechik' (uses precomputation values of the 'gf' function; the performance of the encryption function has increased by an average of 5..10 times)
- Refactoring and code modification in module **gosthash** to increase the performance of hasing (uses precomputation values of the 'l, s and p-transformation', function; the performance of the encryption function has increased by an average of 2..7 times)
- Added the **gostoid** module that implements generating cryptographic object IDs for the **gostcipher**, **gosthash**, **gosthmac** and **gostsignature** modules

- Refactoring **gostcipher** module (changed the class hierarchy to remove code duplication)
- Refactoring **gosthash** module (remove code duplication)
- Fixed some minor bugs
- Updated docstring in accordance with the Google Python Style Guide