iwhois: add README (#7176)

plugins/iwhois/README.md

+# iwhois
+
+Provides a whois command with a more accurate and up-to-date list of whois servers
+using CNAMES, via [whois.geek.nz](https://github.com/iwantmyname/whois.geek.nz).
+
+To use it, add iwhois to the plugins array of your zshrc file:
+```
+plugins=(... iwhois)
+```
+
+### Usage
+
+The plugin defines the function `iwhois` that takes a domain name as an argument:
+
+```
+$ iwhois github.com
+   Domain Name: GITHUB.COM
+   Registry Domain ID: 1264983250_DOMAIN_COM-VRSN
+   Registrar WHOIS Server: whois.markmonitor.com
+   Registrar URL: http://www.markmonitor.com
+   Updated Date: 2017-06-26T16:02:39Z
+   Creation Date: 2007-10-09T18:20:50Z
+   ...
+```

plugins/iwhois/iwhois.plugin.zsh

-# provide a whois command with a more accurate and up to date list of whois
-# servers using CNAMES via whois.geek.nz
-
 function iwhois() {
     resolver="whois.geek.nz"
     tld=`echo ${@: -1} | awk -F "." '{print $NF}'`