add tty_init
rename uvjs_stream to uvjs_tcp

Matches pattern for other file names
move array buffer allocation and management to embedder

Embedder should provide means for allocating resources to uvjs bindings
before using the bindings.
remove old uvjs_buf.h file

We use ArrayBuffers, not the custom buffer.
improve documentation for ArrayBufferAllocator
cleanup test shell code

- format
- remove unused parts