Investigate adding an is_a() function

Since we are a dynamically typed language, its natural that we will want to know what type something is.  We can add a function to do this easily, but the problem is we need a specific type for types!  Yet more keywords would be required for the following:

```
int
float
string
array
function
```

and one or more of the following functions:

```
is_a()
type_of()
```
