Consider deprecating use of the 'guid' gem

[ahukkanen]

It seems that e.g. the creation of process templates (or any model using guids) is broken currently under Windows because of how the guid gem detects Windows. I tested this only with x64 version of Ruby, so not sure if it still works for x86.

I would suggest changing this:
https://github.com/madzhuga/rails_workflow/blob/master/app/concerns/rails_workflow/uuid.rb#L10

Into:

self.uuid = SecureRandom.uuid