Merge pull request #3900 from wp-cli/3728-server-command

Abstract `wp server` back to wp-cli/server-command

Author: schlessera

composer.json

@@ -37,7 +37,8 @@
 		"wp-cli/media-command": "^1.0",
 		"wp-cli/export-command": "^1.0",
 		"wp-cli/package-command": "^1.0",
-		"wp-cli/search-replace-command": "^1.0"
+		"wp-cli/search-replace-command": "^1.0",
+		"wp-cli/server-command": "^1.0"
 	},
 	"require-dev": {
 		"phpunit/phpunit": "3.7.*",