removed Id type changed tag name
if stmt is nil, can't close without panic :(
fixed zero value panic
Update readme
exclude Id column when insert if  Id value is zero
Added WhereEqual method
Suppor string primary key for PostgreSQL
Several Updates

Added "Close" method to close database.
Added "OmitJoin" method to omit join fields in struct.
Added support for multiple order by.
Merge pull request #1 from coocood/master

Sync