Write Commands Specification 0.5 - update multi, delete limit

style and TODO cleanup
RUBY-676
move public methods before private

RUBY-676
concise #op_args_set, #op_push, #initialize_copy Ruby way

Write commands 0.5
RUBY-676
merge Write Commands Specification 0.5
RUBY-614 support for SASL PLAIN authentication (LDAP)
RUBY-614 test coverage for SASL PLAIN support
RUBY-698 adding deserialization options to collection#find and bson