Refactored project to simplify migration and support swift 4.2#1

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wibosco wants to merge 8 commits intomasterfrom

Commits on Jan 8, 2019

Refactored project to simplify migration and support swift 4.2
wibosco
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Further simplified migration by removing unneeded convenience methods
wibosco
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Commits on Jan 13, 2019

Commits on Jan 14, 2019

Added more realistic example
wibosco
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Commits on Jan 15, 2019

Updated unit tests to tear down Core Data stack without warnings
wibosco
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Commits on Jan 18, 2019

Extended example
wibosco
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