CLI command to test connection to Ionic servers

Multiple commands like `ionic upload` or `ionic cordova resources` fail if the command line is not able to connect to Ionic Servers. Often adding proxies might solve the problem, but it would be nice to have a command you can tell people to check this. `ionic check connection` or something similar. (Of course this one command wouldn't justify adding the `check` command with a subcommand, but you get the idea)