nghttp2_hd: Remove unused variables
Update doc
inflate_header_block: Terminate session on compression error

Code cleanup is done as well
Code cleanup
Remove nghttp2_session_continue

nghttp2_session_continue is removed. Now just call
nghttp2_session_mem_recv to continue after NGHTTP2_ERR_PAUSE.
Update doc
Don't call on_request_recv_callback if header decompression failed
doc, examples: Update tutorial and examples