Added inheritance for hooks from parent classes

also added hook inheritance from mixins, and adding
hooks to child controllers, added as sub-controllers.

Fixes bug 1330673

Change-Id: I709cece7bcce26943b254b15dc8ddac5613b1202
Add support for specifying custom request and response implementations.

I noticed that people using pecan have taken to writing custom webob req/resp
subclasses and monkeypatching onto `pecan.request` and `pecan.response`.  Let's
give them what they need to do this properly.

Change-Id: If0ac953e381cec3a744388000a3b3afc0ea2525c
Fix a bug that broke `default_renderer = json`.

Change-Id: Ie57feadb6efe664c1bc3c39debcb21c3355f210c
Fixes bug 1332501
Merge "Added inheritance for hooks from parent classes"
Merge "Add support for specifying custom request and response implementations."
Serialize WebOb errors as JSON if the client requests it via an Accept header.

Change-Id: I32040eff4259daf7a0e58b81ce861758d1d14bd9
Fixes bug 1324134
Merge "Serialize WebOb errors as JSON if the client requests it via an Accept header."