Fixing tests; minor adjustments

[someson]

according to #52 (comment) my job is done, pls check

some notes:

• i don't understand why is there the /types folder, it has nothing to do with purpose of this/parent project. There's carbonphp/carbon-doctrine-types package as an externalization of nestbot/carbon package for this usecase.
• for production (without nesbot/carbon) all the classes in /types folder are not usable (lack of Carbon namespase)
• so I moved the /types to /tests, but what are we testing there, if those classes have no sense in the package? I would remove it completely.