Merge pull request #42 from yinrong/ban-castIds

[bugfix] turn off mongodb auto cast ObjectID

Merge pull request #41 from yinrong/tmp

[bugfix] fix update

Merge pull request #40 from yinrong/mongo-findOneAndUpdate

[feature] mongo findOneAndUpdate & count

Merge pull request #39 from yinrong/mongodb-extend

[feature] support for mongodb extend

Merge pull request #38 from yinrong/mongodb-bugfix

[bugfix] mongodb connection bugfix

Merge pull request #37 from yinrong/support_mongodb

[feature] support backend: mongodb #25

Merge pull request #34 from Bingmang/master

[feature] support Promise/async/await (resolve #26)

bump version