Fix exception page console regression

The regression happened after #67.
Merge pull request #73 from gsamokovarov/fix-exception-page-regression

Fix exception page console regression
:burn: terminal at /console

For the sake of the users, let's not include this in 2.0. It may seem
messy from project history perspective, but let's not put this burden to
the users in 2.0. Closes #70.
Merge pull request #74 from gsamokovarov/kill-terminal-for-good

:burn: terminal at /console
Introduce initial middleware draft
Don't wrap requests in Rack::Response when not needed
Get the original exception in DebugExceptions monkey patch
Prioritize web_console.exception when picking creation scheme

It may happen that application code sets web_console.binding first and
then the app fails. The console pages will spawn a console in an
unexpected binding then.
Add a test to guard for web_console.exception priority
Extract WebConsole::Request for all web-console specific request ops