Replaced DoesRoleTakesARoleName By RoleNameRequired
Wrote tests for exception thrown in Moose::Meta::Class::excludes_role
Wrote common exception class for Moose::Meta::Class excludes_role & does_role
removed throw_error & added throw_exception("RoleNameRequired")
Added lib/Moose/Exception/RoleNameRequired.pm & removed DoesRoleTakesARoleName