Merge pull request #184 from shirou/master

Add DropTableIfExists
Don't check relations if field is ignored
Fix invalid reflect value
Don't raise error when get TableName even Scope has no db
AutoMigrate accepts structs
By default, pluralize table name
Add Set, Get method for DB
Add InstanceSet, InstanceGet fomr Scope
gorm: added ability to change the time.now format
Refact First, Last to make it possible to reset table name in Plugin
Add InstantSet for DB
Fix register callbacks in some cases
Merge pull request #206 from cihangir/master

gorm: added ability to change the time.now format
Use the original DB when create a new Scope
Fixed spelling error
Merge pull request #208 from longnguyen11288/patch-1

Fixed spelling error
update tests
Fix check postgres has table
Add HasTable()
add test for HasTable()