Offer :encode => false option to bypass cookie value escaping

[rack]

Offer :encode => false option to bypass cookie value escaping

[rcrowley]

Further, since Rack::Session::Cookie uses Array#pack to base-64-encode data, "+" is replaced by " " causing sessions to be impossible to unserialize.

[tenderlove]

Rather than use a magic flag, I've made the Cookie constructor take an optional coder parameter. The object supplied in that parameter will be used to encode and decode session cookie data.

Here is a patch with tests and documentation of how to use the coder object.

[cgriego]

@tenderlove The encoder option looks great, but will is also be applied to Rack::Response#set_cookie? You're commit only applies it to Rack::Session::Cookie.

[tenderlove]

Cookies may be configured with an object that will serialize and deserialize the session cookie data. closed by 260fca3, closed by 260fca3