Removed mailgun-php version number

Removed mention of mailgun/mailgun-php's version number on the README.

README.md

@@ -4,7 +4,7 @@ Bogardo/Mailgun
 A Mailgun package for Laravel 4 for sending emails using the Mailgun HTTP API.
 It's main advantage is that the syntax is the same as the Laravel Mail component and I also tried to give it very simmilar functionality. So if you've used that component before, using the Mailgun package should be a breeze.
 
-> This package makes use of the [Mailgun-PHP](https://github.com/mailgun/mailgun-php) library, version 1.7.<br />
+> This package makes use of the [Mailgun-PHP](https://github.com/mailgun/mailgun-php) library.<br />
 
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