Merge pull request #52 from ZhengYang/master

Import logic for code gen
Merge pull request #53 from ZhengYang/master

import package for no-pk models
Merge pull request #54 from ZhengYang/master

add binary data type in mapping
Merge pull request #55 from ZhengYang/master

help message format
Merge pull request #56 from ZhengYang/master

Minor UX improvement before implementing pq
Merge pull request #57 from ZhengYang/master

Generate app code from existing PostgreSQL database
Merge pull request #58 from ZhengYang/master

remove debug code & api usage message
Merge pull request #59 from ZhengYang/master

version++
format the log time
support bit type
support tinyblob  mediumblob
add time type