Changed composer package name to match

[jakedowns]

Looks like the readme package name didn't match the composer package name.
This was causing composer to throw an error:

• The requested package gufran/laravel-authorize-net-cim could not be found in any version, there may be a typo in the package name.

[jakedowns]

Whoops. BrandonMcQueen beat me to it: #1