Support nested folders & Postgres schema

1. Migration files generated by Hasura resides in a directory structure like

   migrations
   ├── 1111111111_one
   │   ├── down.sql
   │   └── up.sql
   └── 2222222222_two
       ├── down.sql
       └── up.sql
   

   So we need #11 to recursively find the up.sql

2. Added support to specify schema for postgres #14

3. Fix problems with make test #12

4. Ignore pq: unexpected transaction status idle error #13