* Changed mongo.go to use new driver
* Modified mongo cataloger
* More new driver related changes
* Change lister.go
* Change saver.go
* Change imports
* Remove unnecessary Count query
* Use IndexView for indexing
* Rename ModuleStore fields
* Use map of key:sorting-order for creating the index
* Minor changes
* Use client options to configure mongo client
* Use method chaining
* gofmt changes
* Change imports
* Fix some build errors
* Use new GridFS API
* Fix more build errors
* Add Go Mongo driver to dependency modules
* Use multierror
* Leave download stream open
* Remove mgo error handling
* Copy zip instead of loading all in memory
* Use context.WithTimeout() wherever possible
* Raise KindNotFound when mod@ver isn't found
* NopCloser not needed
* Fix IndexView error
* Fix build errors
* Remove another mgo error usage
* Fix build error
* Changes according to review
* Formatting changes as per gofmt
* Modify gofmt argument to show the expected formatting (diff)
* Handle ErrNoDocument error and error arising from query execution
* Fix kind of returned error
* Minor changes
* Bug fixes
* gofmt related changes
* Minor change
* Use Insecure from MongoConfig, remove Insecure from global Config
* Remove stray print statement
