Cache should have dictionary-like syntactic sugar

[maniksurtani]

The Cache class uses Java Map-style put(), get(), remove() and contains(). Which is fine, but we should also offer Python-style syntactic sugar, so that we can do:

cache['key'] = 'value'
print cache['key']
if 'key' in cache:
  print 'Key exists!'
for e in cache:
  print e

etc. Have a look at the implementation of a Python map for more details, or one of the many custom map-like classes available for Python.

This is usually implemented by defining internal methods, such as:

def __getitem__(self, key):
  return self.get(key)

def __setitem__(self, key, value):
  self.put(key, value)

etc.