* Go flagless to allow custom user defined flags. Fixes#301
* Add --cache-dir flag for cache plugin (when used with on-disk store)
* Enable discovery of flags from external plugins, example those that reside outside of proxy.py package and loaded on demand. This also allows external flags to surface in --help section
* Define --filtered-client-ips flag for FilterByClientIpPlugin
* Allow plugins to add custom command line flags. Addresses #301
* Reduce dependency over Flags class. This will be deprecated so that adhoc flags can be added without any additional manual configuration
* Fix: Argument 1 to "mock_default_args" of "TestMain" has incompatible type "Namespace"; expected "Mock"
* Reduce Flags class to just the initializer.
* Store list of action dest in FlagParser
* Better document acceptor module and add a TCP Echo Server example
* autopep8 formating
* Rename ThreadlessWork --> Work class
* Make initialize, is_inactive and shutdown as optional interface methods.
Also introduce Readables & Writables custom types.
* Move websocket code into its own module
* Add websocket client example
* Cleanup websocket client
Aksh Gupta