add IO layer option to Log::Any::Adapter::File

when message needed to be logged are wide char, use this Log::Any::Adapter::File will warning : 

wide charactor ..... 

by perl. 

to avoid this warning, user need to encode their message to be encoded, then to log out to file.

this may not be convenience, so I think this module can add some interface / arguments, let user set the IO layer : 

such as set ':utf8' IO layer, which will be work for logging out utf8 message and no need to encoding it before.

thanks :)