Do not use Rack::Chunked by default, leave the option to the user
Expose Rack's map method for low level url mapping
Bump version
Document map in readme
Update assets example
Merge remote-tracking branch 'origin/master' into release-3.4.3
Update changelog
Note about the map block
Bump actionpack dependency
Note in readme about actionpack
Merge pull request #64 from alisnic/release-3.4.3

Release 3.4.3