Add some extra TestSoundCases

[JD557]

Adds some extra test sound cases to increase the test coverage.

This brings the SoundexAlgo coverage close to 100%, but unfortunately I don't know enough about the algorithm to trigger the missing edge cases.

This also improves the MetaphoneAlgo coverage, but again, since I'm not very familiar with the algorithm, it's hard to generate the edge cases.

I also removed a String -> Array[Char] conversion to improve the test coverage. I also think that this might slightly improve performance (since the conversion happens later, and only if needed), but I haven't benchmarked it.

[coveralls]

Pull Request Test Coverage Report for Build 229

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.9%) to 97.326%

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Totals
Change from base Build 228:	1.9%
Covered Lines:	364
Relevant Lines:	374

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💛 - Coveralls

[vickumar1981]

Relates to issues:

• https://github.com/vickumar1981/stringdistance/issues/55
• https://github.com/vickumar1981/stringdistance/issues/56