Compress the data before sending over the network

[green-coder]

(Based on the feedback from @plexus w.r.t. the http PATCH use case)

The data representation of the diff was chosen for its user friendliness and its efficiency during composition. It is relatively verbose for been send over the network.

The data could potentially be encoded into something smaller. We could add some serialize / deserialize functions to compress it. For instance:

• in maps, keys could be grouped by operations, similarly to the sets.
• in vectors, the index-ops could be flattened 1 level, a :replace operation could replace a :remove followed by an :insert.