Restructure/Refactor test cases

[vickumar1981]

The class that stores test case information needs to be refactored:

https://github.com/vickumar1981/stringdistance/blob/master/src/test/scala/fixtures/TestCases.scala#L6

TestCase and TestSoundCase are case classes with value members: Option[T] where T is either an Int or Double depending on whether the test is for a distance or fuzzy score metric. These classes need to be generalized to support adding more test cases with greater flexibility.

String and String sound tests may need to be refactored as well to support any new model:

https://github.com/vickumar1981/stringdistance/blob/master/src/test/scala/TestStringDistance.scala

https://github.com/vickumar1981/stringdistance/blob/master/src/test/scala/TestStringSoundScore.scala