Update readme

Author: Nico

README.md

@@ -22,7 +22,7 @@ Find me on Twitter: @[nicoSWD](https://twitter.com/nicoSWD)
 Via Composer
 
 ```bash
-$ composer require "nicoswd/php-rule-parser": "0.3.*"
+$ composer require "nicoswd/php-rule-parser": "0.4.*"
 ```
 
 Via git
@@ -85,7 +85,7 @@ $variables = [
 $rule = new Rule($ruleStr, $variables);
 
 $rule->registerToken(Tokenizer::TOKEN_GREATER, '\bis\s+greater\s+than\b');
-$rule->registerToken(Tokenizer::TOKEN_VARIABLE, ':\w+');
+$rule->registerToken(Tokenizer::TOKEN_VARIABLE, ':[a-zA-Z_][\w-]*');
 
 var_dump($rule->isTrue()); // bool(true)
 ```