Merge branch 'v2-issue-91' into v2

README.md

db.go

db_test.go

error.go

mongo/collection.go

mongo/connection.go

mongo/connection_test.go

mongo/database.go

mongo/database_test.go

mongo/id.go

mongo/result.go

mysql/collection.go

mysql/connection.go

mysql/connection_test.go

mysql/database.go

mysql/database_test.go

mysql/template.go

net.go

postgresql/collection.go

postgresql/connection.go