added new test class for operators & moved test cases to it
removed swapElementByOne method & removed test of it
Operators test cases added in another class
The program is modified to have a state as wholeExpression and use it
parser class created to convert expression in evaluatable format
Parser class seperated from ExpressionEvaluator & created test file for it
Parser tests added
Expression class added
classes changed according to Expression class
main changed to work with expression
scanner class added & test added for scanner
parser changed as per the scanner
expression & its tests changed according to scanner