Improve errors from weather

[fhunleth]

weather is being used to check if the internet works on Nerves. Giving better error messages when the network doesn't work or DNS fails would be helpful.

[mnishiguchi]

How about ping once within the weather/0 to check the network? We could repurpose tping/2's logic.

toolshed/lib/toolshed/tcp_ping.ex

Lines 29 to 36 in fba8e62

	case resolve_addr(address) do
	{:ok, ip} ->
	port = Keyword.get(options, :port, 80)
	ping_ip(address, ip, port, connect_options(options))
	{:error, message} ->
	IO.puts(message)
	end

[fhunleth]

I think that I should have been more specific when writing this up. If I remember right, if you don't have internet access and try running weather, you get an exception. I was just thinking that it would be nice to catch the exception or translate the error into a friendlier message. I don't think that any network diagnostics need to be done.