Adde function #'check-last-error and use it in #'insert-op,
#'update-op, #'delete-op
Added variable *auto-check-last-error*

If the value of this variable is T (default) then #'check-last-error
called after calls #'insert-op, #'update-op, #'delete-op.
Library has been redesigned.

Added support for the adapters. Available adapters:

  * usocket (bloccking)
  * cl-async (experimental)

Added class 'server-config:

  (mongo:make-instance 'server-config :host host :port port)

Added support for Write Concern
(http://docs.mongodb.org/manual/core/write-operations/#write-concern):

  (make-instance 'mongo:write-concern
                 :w :receipt-acknowledged
                 :j t
                 :fsync t
                 :wtimeout 100)

Added class mongo-client. For creation of 'mongo-client, use
mongo:create-mongo-client:

  (mongo:create-mongo-client :usocket :server config :write-concern w)

Many different other changes.