Use method_missing instead of that class_eval / instance_eval as to not clobber module level variables
This piece of code is a bit disgusting. We will clean it up soon,
but basically, we were creating closures using this code snippet
but those closures were transferred to the actual classes themselves
so you would have something like BankAccount.new.account and this
will give the last closure added for a BankAccount even if it has
nothing to do with the actual class itself.

This caused some weird errors, so the best thing to do was to just
move this piece of code and "dynamically" enable it for all
method requests that are essentially #{method}_uri.

This solves the acute problem, for now.
Merge pull request #108 from balanced/method-missing

Method missing