Move util functions to github.com/naoina/kocha/util package
Move GenerateRandomKey() to github.com/naoina/kocha/util package
Change to unexported the NewRequest()
Change to unexported the NewResponse()
Change to unexported the (Forward|Reverse)Router
Change to unexported the Result* structs
Change to unexported the Router struct
Chagne to unexported some template types
Change to unexported the MethodArgs type
Merge branch 'improve/refactoring'