Streaming mode support

[syakunin]

Library should support streaming mode for encrypting large files on-the-fly. Several issues with streaming:

1. We will not be able to use deterministic CID in streaming mode, because deterministic CID requires to calculate data hash to create encryption key. This means we will need to read the stream twice. First pass is for calculating hash and creating encryption key, second pass is for encryption with calculated key.
2. Currently WebCrypto supports only in-memory mode hashing/encryption. However NodeJS allows to hash/encrypt data in streaming mode. We might restrict streaming mode only to NodeJS users or we need to find alternative hashing/encryption libraries for streaming in browser (they will not be so fast as native ones). One of the good candidates is hash-wasm library, which can perform stream hashing in browser and in NodeJS.