start of FractionCalculator and FractionCalculatorTest
clean up test code
FractionCalculator: main(), launch(), evaluate()

Added the main method in which I put a launch method. started evaluate()
evaluate() changes

added spilt to evaluate() and introduce a for-loop to loop through the
newly created array
evaluate () changes

split the input string into array which is looped with a for loop
added field - operator, more code in evaluate(), error()

added a new field that will store the current operator and will carry
over to a new operation when needed. Evaluate() now initialised the
required new fraction to return which will be initially set with the
values of the passed fraction as a parameter - this will ensure the
value of the previous calculation carries over too. Error () for now
prints an "error" message
else if expansion

added the checks for all operators
testing the operator

this test inputs an operator as a string and prints it. Then "it tries"
to add another consecutive operator which is not executed and results in
an error
else if expansion - operation with fractions

expanded the code to include identification of fractions in the string
input. It checks if there is an operator or not - if yes, then the
operation is executed. If not, then the value of the calculator becomes
the newly found fraction.
I made the fields public (temporarily) so that I can access them from my
FractionCalculatorTest class.
Also decided to remove isEmpty () boolean check and turn it
(operator==null).