[FIX] single export TypeError: cannot read properties error

[debdutdeb]

closes #41

[d-gubert]

The PR solves that issue, but disregards the comments in the class file:

          * However, we need to handle this case due to backwards compatibility,
          * since the main class file might export a class with an unknown name,
          * which was supported in the early versions of the Apps-Engine.

Which causes apps that don't follow the convention of naming their classes the same as their files to break.

A solution I've found to all these problems is to simply change the if statement in the compiledRequire function as follows:

        if (Object.keys(exports).length === 1 && typeof result === 'function') {
            return result;
        }

This way we are handling the older cases more specifically while fixing the problem.

The other changes are not needed.

@debdutdeb can you apply these changes to the PR? :)