Replace UTF-8 with app charset
Rename protected methods in Kelp

In order to minimize confusion, the request and response methods were
renamed to build_request and build_response. This breaks backwards
compatibility for those who have designed custom request of response
objects. They will have to rename their methods too.
Replace message with shortcut 'info'
Add access to app from the config

The config module now has access to the app instance, via the 'app' sub.
Rename pattern attribute 'via' to 'method'

For clarity and semantic compatibility, the pattern attribute 'via' is
now legacy and the attribute 'method' should be used instead.
'via' will continue to be supported, as a shortcut to 'method'.