Make MySQL the default connection type incase the project's connection type is different.

[PhillipMwaniki]

PR Naming convention

BUG: Fix to error Undefined variable $className

Issue or feature explanation

Currently, if the user doesn't use the Laravel's default connection types, an error is thrown Undefined variable $className

This PR fixes Issue https://github.com/Protoqol/Prequel/issues/165

Proposed solution/change

Make MySQL the default connection in case the package can't find one of the default's connection types.