add function to convert host parameters to hostname

lib/to-host.js

@@ -0,0 +1,17 @@
+import { parse } from 'url';
+
+/**
+ * Converts a valid deployment lookup parameter to a hostname.
+ * `http://google.com` => google.com
+ * google.com => google.com
+ */
+
+export default function toHost (url) {
+  if (/^https?:\/\//.test(url)) {
+    return parse(url).host;
+  } else {
+    // remove any path if present
+    // `a.b.c/` => `a.b.c`
+    return url.replace(/(\/\/)?([^\/]+)(.*)/, '$2');
+  }
+}