In this set of exercises, you are to implement a class named <code>Even_Num</code> that represents even integers. The invariant/constraint/rule for this
class is that no object is ever allowed to contain an odd value. You are to code the .h file and the .cpp file (two separate questions).
<p>
The usual set of functions/operators:

<ul>
	<li>A constructor that accepts an integer (defaults to 0) and uses it to initialize the object
	<li>A &lt;&lt; operator that simply prints out the value of the object
	<li><code>+</code> and <code>+=</code> operators
	<li><code>/</code> and <code>/=</code> operators
	<li>a <code>get<code> method
</ul>

The usual rules: 

<ul>
	<li><code>+=</code> and<code>/=</code> should be members
	<li><code>+</code> and<code>/</code> should be non-members (you can make them friends or not)
	<li><code>get</code> should be a const member function
	<li>the usual parameter transmission conventions
</ul>