Issue #24 fix character classes

[zoltanmaric]

Fixes #24. Apart from including the missing characters (z, Z, and 9) in their respective classes and filters, this change should yield equal results as the upstream version.

I didn't want to change the functionality drastically not to break existing code, but this trait is actually reinventing the character classes already available on Scala's Char class. These include isLower, isUpper, toLower, isLetter,isDigit`, etc.

I would suggest deprecating this trait and use the following existing alternatives (compatible with the StringTransform type):

• _.filter(_.isLetter) instead of filterAlpha
• _.filterNot(_.isLetter) instead of filterNotAlpha
• _.filter(_.isDigit) instead of filterNumeric
• _.filterNot(_.isDigit) instead of filterNotNumeric
• _.filter(_.isLetterOrDigit) instead of filterAlphaNumeric
• _.filterNot(_.isLetterOrDigit) instead of filterNotAlphaNumeric
• _.filter(_.isLower) instead of filterLowerCase
• _.filterNot(_.isLower) instead of filterNotLowerCase
• _.filter(_.isUpper) instead of filterUpperCase
• _.filterNot(_.isUpper) instead of filterNotUpperCase
• _.map(_.toLower) instead of ignoreAlphaCase

They are not equivalent, but they are part of the standard library, and I would argue that they are much more accurate than the existing filters.