Should use class methods instead of plain subs

[eyadof]

We have a couple of methods in RPC/Message.pm that are factory-style subs:

• https://github.com/binary-com/perl-Myriad/blob/master/lib/Myriad/RPC/Message.pm#L162
• https://github.com/binary-com/perl-Myriad/blob/master/lib/Myriad/RPC/Message.pm#L195

as per @tom-binary this is a problem as we should not mix plain subs and methods in the same package:

we should make them class methods like:

use Object::Pad;
 class Example { 
   sub new_from_something ($class, %args) { 
     return $class->new(%args)
   }
} 
Example->new_from_something()