Added Malayalam wiktionary parsing code
Major refactoring of the code

* wiktionaryparsers/knwikiparser.py: Moved _prepare_message as
  prepare_message in base class. This should normally be common for all
  parsers, but if needed should be override in derived class
* wiktionaryparsers/wiktionaryparser.py: meanings dictionary should be
  part of base class use __slots__ to declare class
  variables. prepare_message can now handle even if wiktionary page
  doesn't have word type.
* bridge.py: Implement MLWiktionaryParser and generating proper
  formatted message for client is now done by Bridge instead of
  Parsers. Parsers now simply return a dictionary with meanings.
Updated README.md