Bring the REPL adapters from the 0.2 fame

During this GSoC, we would like to focus our efforts on making the web-console introspect the current process and possibly to integrate itself into the default Rails error pages. To do that we need a mechanism to execute Ruby code in an arbitrary binding. Luckily, we already have some code from the 0.{1,2} days, that used to do that and we can reuse it as a start.