Functions: init - will initailze the Calculator functionality
bindEvents - will take care of all the click events
displayChars - will display the characters in the text box
displayResult - displays the result in the text box
resetOperand - to reset the operand and operator
add - receives the inputs from equals function to perform additon
subtract - receives the inputs from equals function to perform subtraction
multiply - receives the inputs from equals function to perform multipliction
divide - receives the inputs from equals function to perform division
clear - to reset the calculator