changed IO method to add encoding of the separate collections and checks that the file exists or create a new file
changed newContact to not return a contactId(was incorrect)
changed addNewContact to not return anything(as required by specification)
cleaned up tests by introducing methods for generation of contact lists
changed tests that relied on retrieving contacts by Id to use a different method(getContact by name)
due to error messageMerge branch 'master' of https://github.com/LiliyaStefanova/ContactManager