[Stack] Stack implemenation added
[Stack] Addedd README.md for Stack kata
[RomanNumeralConverter] Conversion of units added
[RomanNumeralConverter] Conversion of tens added
[RomanNumeralConverter] Conversion of hundreds added
[RomanNumeralConverter] Conversion of thousands added
[RomanNumeralConverter] Conversion of complex numbers added
[RomanNumeralConverter] Refactoring - removed conversion tables, added Stream API
[RomanNumeralConverter] Handling exceptions added
[Stack] Update README.md
[Stack] Update README.md