[Web] Unable to find en-us?

[Autrijus Tang]

Some people (like me) use en-us instead of en as ACCEPT_LANGUAGE. 
Currently the homepage will show

"We were unable to find [en-us] translation(s) of this document. We 
have provided a translation in English instead. For more information 
on translations look here."

Which is quite counter-intuitive. May I suggest a default fallback to 
the first two-letter if it's available? That way, zh-sg can fallback 
to zh reliably.

Thanks,

/Autrijus/Y��j)b�       b�՞m��zw���#y�h�m����.���z�(����Y���b�ا~��y