Refactor test file using contexts
Refactor code: now Modula is not singleton
Fix export & require description in tests
Add register function
Convert Modula to class
Implement Modula::exportToWindow function

It allows to export all or selected modules to window.
Rearrange order of public functions
Merge pull request #7 from kossnocorp/feature/3-register_function

Modula::register & Modula::exportToWindow functions (closes #3)