Add a keyword arg 'use-cl-debugger' to 'clackup'. If it's NIL, it'll use clack-errors.
Add a keyword arg 'watch' to 'clackup'.
Change the rule of version numbers.

They are used to be decided from the release date (ex. 2012-08 -> v12.08.0).
But it causes a warning "Invalid :version specifier" of ASDF.

This is changing the rule of version numbers of all Clack asd files.
Their versions are roughly decided from their history.
Drop 'w' from my name.
Stop binding *clack-output* & *clack-error-output* when loading clack.
Add 'wrap' for 'function's.
Add Clack.Middleware.Accesslog.