Print errors to stderr instead of stdout

[glinton]

trafficstars

If the output is piped, the error can get lost:

$ nanobox log fakeapp | grep thing
$

Error going to stdout currently:

$ nanobox log fakeapp

! Sorry, the app 'fakeapp' doesn't exist


Error   : Not Found ({})
Context : unable to validate app -> Unknown app 'fakeapp'
Suggest : It appears that app or component wasn't found, check the team/app name and try again