Revert "wrapping MethodContext before loading"

This reverts commit 59b62d4500551017fd36ce77542a338e56d1b5d8.
late fn rebinding; cleaner solution to Error handling

Reverts fix from few days ago that has broken load/runtime
separation and fixes error handling by taking fn into account
when redefining classes, enabling later fn injecting.
Merge pull request #596 from herby/late-fn-inject

Late `fn` inject - cleaner solution to error handling