creating private messaging

[remiboivin-zz]

Creating a private messaging for members

[gathuku]

class User
  has_many :conversations, thorough: :user_conversations
   has_many :messages
end

class Conversation
 has_many :users through: :user_conversations
 has_many :messages
end

class Message 
  belongs_to :user 
  belongs_to :conversation
end

class UserConversation
  belongs_to :user 
  belongs_to :conversation
end

[gathuku]

@remiboivin please review