Add a failing test for #35
Don’t throw error exceptions for all errors.

When including or executing in the execution loop, only throw error exceptions for errors above the current error_reporting threshold.

Log the rest for posterity, but let the code finish anyway.

Fixes #35
Make non-error errors a bit nicer.

Always style errors below the current reporting threshold as warnings.

See #35

Styles E_NOTICE and E_USER_NOTICE as warnings as well.