Changed incorrect instances of 'arguments' to 'parameters'

When writing a method's signature (declaring the method), the values being passed to a method are called `parameters`, not `arguments`. When calling a method, the values passed to the call are formally known as `arguments`. This is a general misnomer in the programming community. I've corrected all relevant instances.

Example of parameters:
```
def some_method_with_parameters(param1, param2)
    param1 + param2
end
```
Example of arguments:
```
some_method_with_parameters(1, 2)
```
Same here. "Parameter mutation" sounds a bit strange to me.