Step nr. 4 complete. Refined the class Calculator and decided to keep the delimiters in a string variable, which is used as a parameter in the split function.
So if we add another delimiter, the delimiter string will be updated in the split function.
Added to test cases, to check the new functionality.
.
Merge branch 'master' of github.com:gislirafn/String-Calculator

Conflicts:
	src/test/java/is/ru/stringcalculator/CalculatorTest.java