fix warning message

lib/fork.js

@@ -11,7 +11,7 @@ var doSend = require('./send');
 if (fs.realpathSync(__filename) !== __filename) {
 	console.warn(
 		'WARNING: `npm link ava` and the `--preserve-symlink` flag are incompatible. ' +
-		'We have detected that AVA is linked via `npm link`, and that your are using either using ether ' +
+		'We have detected that AVA is linked via `npm link`, and that you are using either ' +
 		'an early version of Node 6, or the `--preserve-symlink` flag. This breaks AVA. ' +
 		'You should upgrade to Node 6.2.0+, avoid the `--preserve-symlink` flag, or avoid using `npm link ava`.'
 	);