Merge pull request #33 from jeremykendall/fix/issue-32

Adds ext-intl to composer "require" key, updates README.  Closes #32.

Author: jeremykendall

README.md

@@ -121,6 +121,9 @@ $publicSuffix = $url->host->publicSuffix;
 support was added in version `1.4.0`. Both unicode domains and their ASCII equivalents
 are supported.
 
+**IMPORTANT**: PHP's [intl](http://php.net/manual/en/book.intl.php) extension is
+required for the [IDN functions](http://php.net/manual/en/ref.intl.idn.php).
+
 #### Unicode
 
 Parsing IDNA hosts is no different that parsing standard hosts. Setting `$host = 'Яндекс.РФ';` (Russian-Cyrillic)

composer.json

@@ -20,7 +20,8 @@
     ],
     "require": {
         "php": ">=5.3.0",
-        "ext-curl": "*"
+        "ext-curl": "*",
+        "ext-intl": "*"
     },
     "require-dev": {
         "mikey179/vfsStream": "1.2.*",