Disambiguate "the BSD license"

[A Wikipedia article](http://en.wikipedia.org/wiki/BSD_licenses) says "the BSD license" means [the 3-clause BSD license](http://opensource.org/licenses/BSD-3-Clause), as quoted below,

> This [3-clause] version has been vetted as an Open source license by the OSI as the "The BSD License".[3]

while the link provided in the footnote now redirects to [the 2-clause BSD license](http://opensource.org/licenses/bsd-license.php).

Assuming you really meant the 2-clause license, this commit clarifies the term so that someone (including myself) can use this excellent library without hesitation.