Add a `whois` rule
diff --git a/thefuck/rules/whois.py b/thefuck/rules/whois.py
new file mode 100644
index 000000000..f019758ec
--- /dev/null
+++ b/thefuck/rules/whois.py
@@ -0,0 +1,30 @@
+from urllib.parse import urlparse
+
+
+def match(command, settings):
+    """
+    What the `whois` command returns depends on the 'Whois server' it contacted
+    and is not consistent through different servers. But there can be only two
+    types of errors I can think of with `whois`:
+        - `whois https://en.wikipedia.org/` → `whois en.wikipedia.org`;
+        - `whois en.wikipedia.org` → `whois wikipedia.org`.
+    So we match any `whois` command and then:
+        - if there is a slash: keep only the FQDN;
+        - if there is no slash but there is a point: removes the left-most
+          subdomain.
+
+    We cannot either remove all subdomains because we cannot know which part is
+    the subdomains and which is the domain, consider:
+        - www.google.fr → subdomain: www, domain: 'google.fr';
+        - google.co.uk → subdomain: None, domain; 'google.co.uk'.
+    """
+    return 'whois' in command.script
+
+
+def get_new_command(command, settings):
+    url = command.script.split()[1]
+
+    if '/' in command.script:
+        return 'whois ' + urlparse(url).netloc
+    elif '.' in command.script:
+        return 'whois ' + '.'.join(urlparse(url).path.split('.')[1:])

What the `whois` command returns depends on the 'Whois server' it contacted and is not consistent through different servers. But there can be only two types of errors I can think of with `whois`:
- `whois https://en.wikipedia.org/` → `whois en.wikipedia.org`;
- `whois en.wikipedia.org` → `whois wikipedia.org`.

So we match any `whois` command and then:
- if there is a slash: keep only the FQDN;
- if there is no slash but there is a point: removes the left-most subdomain.

We cannot either remove all subdomains because we cannot know which part is the subdomains and which is the domain, consider:
- www.google.fr → subdomain: www, domain: 'google.fr';
- google.co.uk → subdomain: None, domain; 'google.co.uk'.
