Implement CurrencyList

CurrencyList

A suffix tree based CurrencyList implementation.

See #5 (closed) for more information about the used data structure.

CurrencyListTest

Preliminary unit tests for CurrencyList.

These test that:

• getCurrencies returns the expected number of results for various search queries and values added via addCurrency
• Different case variants return the same results
• Existing currencies get overwritten by new entries of the same name
• null arguments result in the expected NullPointerException

I'm testing the class as a whole since the interlocking dependencies of addCurrency and getCurrencies prevent meaningful testing of the individual components.