Added extra basic maths operators

Added the modulus, exponentiation, increment and decrement operators after the 'Maths' section. These are basic and commonly used maths operators in JavaScript. To avoid having too many examples in one example snippet and allow for easily digestible information, I've added a new sub-heading called 'More Maths' to contain these new examples.

Author: TomHodson91

js/lesson2/tutorial.md

@@ -81,6 +81,36 @@ console.log('Division: x / y = ' + division);
 
 > Why not try some other maths problem using the `x` and `y` variables?
 
+#### More maths
+
+Other basic but useful math operators are `%`, `**`, `++` and `--`:
+
+> The modulus `%` operator returns the remainder when dividing one operand by another.
+
+> The exponentiation `**` operator returns the result of raising the first operand to the power of the second.
+
+> The increment `++` and decrement `--` operators return the result of adding one and subtracting one from an operand respectively.
+
+```js
+var x = 5;
+var y = 3;
+var modulus = x % y;
+
+console.log('Remainder: x % y = ' + modulus);
+
+var exponentiation = x ** y;
+
+console.log('Exponentiation: x ** y = ' + exponentiation);
+
+var increment = x++;
+
+console.log('Increment: x++ = ' + increment);
+
+var decrement = y--;
+
+console.log('Decrement: y-- = ' + decrement);
+```
+
 #### Comparisons
 
 The `===` operator compares two values, it returns the boolean `true` if they are equal and `false` if they are not.