zorm 1.2.8 发布，附 zorm 与 gorm xorm 的性能压测结果

 2000 times - Insert zorm: 9.05s 4524909 ns/op 2146 B/op 33 allocs/op gorm: 9.60s 4800617 ns/op 5407 B/op 119 allocs/op xorm: 12.63s 6315205 ns/op 2365 B/op 56 allocs/op 2000 times - BulkInsert 100 row xorm: 23.89s 11945333 ns/op 253812 B/op 4250 allocs/op gorm: Don't support bulk insert - https://github.com/jinzhu/gorm/issues/255 zorm: Don't support bulk insert 2000 times - Update xorm: 0.39s 195846 ns/op 2529 B/op 87 allocs/op zorm: 0.51s 253577 ns/op 2232 B/op 32 allocs/op gorm: 0.73s 366905 ns/op 9157 B/op 226 allocs/op 2000 times - Read zorm: 0.28s 141890 ns/op 1616 B/op 43 allocs/op gorm: 0.45s 223720 ns/op 5931 B/op 138 allocs/op xorm: 0.55s 276055 ns/op 8648 B/op 227 allocs/op 2000 times - MultiRead limit 1000 zorm: 13.93s 6967146 ns/op 694286 B/op 23054 allocs/op gorm: 26.40s 13201878 ns/op 2392826 B/op 57031 allocs/op xorm: 30.77s 15382967 ns/op 1637098 B/op 72088 allocs/op