fix article

l.815
before: An endpoint MUST NOT send frames other than than <x:ref>HEADERS</x:ref> or
fix: An endpoint MUST NOT send frames other than <x:ref>HEADERS</x:ref> or
fix article

before: a HTML
fix: an HTML
fix article

before: a END_STREAM
fix: an END_STREAM
fix article

before:any frame type
fix:any frame types
fix article

before: any frame
fix: any frames
Merge pull request #412 from shotsky/master

Yeah, my grammar really is that bad.