Auto re-connect when connection is closed

[linmao-song]

This attempts to fix #1354 by automatically reconnecting every second.

Manually tested with the following steps:
Start up a proxy script that forwards port 9999 to 8546 (Originally by )

export LC_CTYPE=C
export LANG=C

TMP=mktemp -d
BACK=$TMP/pipe.back
SENT=$TMP/pipe.sent
RCVD=$TMP/pipe.rcvd
trap 'rm -rf "$TMP"' EXIT
mkfifo -m 0600 "$BACK" "$SENT" "$RCVD"
sed 's/^/ => /' <"$SENT" &
sed 's/^/<= /' <"$RCVD" &
nc -l 127.0.0.1 "$SRC_PORT" <"$BACK" | tee "$SENT" | nc "$DST_HOST" "$DST_PORT" | tee "$RCVD" >"$BACK"

Run the following
node
> const Web3 = require('web3');
> const web3 = new Web3('ws://localhost:9999')
> web3.eth.getBlock('latest').then(console.log)
This should print out the latest block. Now kill the above proxy script. Re-do:
> web3.eth.getBlock('latest').then(console.log)

This should print
> (node:48280) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: connection not open

Now start up the same proxy again and repeat
> web3.eth.getBlock('latest').then(console.log)

This will print out the latest block again.

Unfortunately, it doesn't seem easy to add a unit test case for this.

[frozeman]

In order to create tests you would need to create stubs for the ws.connect function and fire ws.onclose.
Does it still works when you try to call a function multiple times, but the connection is not active again?
Will .onclose be also called if the connection couldn't be successfully established?