Use Connectable observable for signalling client

[vkkhare]

A better way is to allow the user to have access to observer and let him subscribe to it as per his use case. This will be a more reactive approach for the user of lib as well.

Additionally this will allow us to have parallel subscriptions to socket channel. But, we would need to decide when to dispose the connections as some subscribers would be just UI based subscribers who will have less priority in deciding whether the connection to pygrid should exist or not. So a simple rxjava:refcount wont work for us

[vkkhare]

with #19 this would require its implementation to be done in syft.kt which will be handling the subscribers

[vkkhare]

#51 implements this