Added a replace function to remove any trailing slashes on the prefix.

[Eliasyoussef47]

I need this addition to prevent any accidental trailing slashes in the prefix variable.
I might use this package this way:

<meta name="asset-url" content="{{ asset('') }}">

and the asset() helper function from Laravel generates a trailing slash (a slash at the end of the url).

[stevethomas]

Looks good! Thanks for contributing.