Katakana SpellCheck Validator #55
adding KatakanaSpellCheckValidator to SentenceIterator.
separeated testDistance in LevenshteinDistanceTest into each topics.
fixed the indentation.
adding a period and changed the comment setntence.
removed the tailing space.
adding private constructor.
changed the name of the static variable, and introduced public static DEFAULT_ variables and initialized the staic variables by them in static initializer.
Adding period.
removed the tailing space.
adding the comments of the public constant variables.
updated License to Apache 2.0
Merge pull request #103 from jmoriya/katakana-spellcheck-validator

Katakana SpellCheck Validator #55