Merge branch 'feature/sqlgen' into v2

.travis.yml

db.go

db_test.go

error.go

mongo/database_test.go

mysql/_dumps/Makefile

mysql/collection.go

mysql/database.go

mysql/database_test.go

mysql/mysql.go

mysql/result.go

mysql/template.go

postgresql/_dumps/Makefile

postgresql/_dumps/structs.sql

postgresql/collection.go

postgresql/connection.go

postgresql/database.go

postgresql/database_test.go

postgresql/postgresql.go

postgresql/template.go