Adding some usage examples to the readme file
Retry blocking system calls on interruption

Recv, send and close may block for a long time, and the kernel
interrupts any blocking system call whenever the process receives
a signal. This didn't happen in the REPL, but in a real app any
blocking call would throw an excption very quickly.

I've made the error handler for close retry on EINTR and EAGAIN, while
recv and send, in addition to coping with interrupts, also forward
the library's ready to receive/send file descriptors to the scheduler.