Accept locales which only match RFC2616 format

[kostyantyn]

http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4

[DouweM]

The HTTP 2.0 (HTTPbis) draft explicitly specifies it will use Language Tags as defined by RFC5646 for the Accept-Language header, which does explicitly mention tags like "es-419".

As pull request #33, this StackOverflow question, this issue and this bug report show (these are the first couple of Google search results), there is a practical need to already support this now, as browsers are already sending these tags to servers implementing HTTP 1.x.

After all, the point of this gem isn't to be a perfectly compliant implementation of RFC2616, but rather to be practically useful to determine what localization the user is likely looking for. If this includes slightly straying from the original RFC and the algorithm proposed therein (as we're already doing, as described in the readme), I will happily do so.

Thanks for your patch, but I will not merge it in this form. If you think there are practical reasons I should reconsider, I would gladly hear them.