def decrement(key, amount = 1, options = {})
      invoke(:decrement, key) do |store|
        alter(store, key, -amount, options)
      end
    end
def decrement(key, amount = 1, options = {})
      invoke(:decrement, key) do |store|
        alter(store, key, -amount, options)
      end
    end
Decrement a key in the store.

 If the key doesn't exist it will be initialized at 0. If the key exists
 but it isn't a Fixnum it will be coerced to 0. Like `increment`, this
 does not make use of the native `decr` or `decrby` commands.

 @param [String] key Key for lookup
 @param [Fixnum] amount Value to decrement by
 @param [Hash] options Optional overrides

 @example

   cache.write('counter', 20) # => 20
   cache.decrement('counter') # => 19
   cache.decrement('counter', 2) # => 17