17 - add support for unix sockets, the default configuration for docker

Made unix sockets the default configuration and usage for the client library to reflect the changes made in 0.5.2. 

This change uses the hook in the requests Sessions object to associate `unix://` paths with a set of custom pools and connections. 

The goal was to patch with as much reuse and interface compatibility to make the changes seamless to the end-user and so as to not introduce regressions on existing functionality.