Completed Step 1 for.php exercise

Asks the user to input a starting and ending number. Displays the
numbers from start to end using a for loop.
Completed Exercise 2 highlow.php

Added feature to allow player to pass two arguments, that are numbers
to create their high/low range. Updated comments. Added if/else at end
if player gets it right on the first guess.
Completed Step 2 for.php exercise

Added prompt for user to choose their increment/decrement. Added loop
for counting down. Nested the game in a do-while for instances of
incorrect inputs by user.
Completed Step 3 for.php exercise

Added default increment of 1 if no input was entered by the user to set
an increment.