SwiftNIO HTTP/2 1.8.0

SemVer Minor

• Issue #151 Update BadStreamStateTransition to have stream state (#175, patch credit to @blueeor)
• Add a subscript to HPACKHeaders to return the first value with a matching name (#178)

SemVer Patch

• Update Code of Conduct project maintainer email address (#176)
• Account for window size of stream closing frames (#174)