bogdan/datagrid — pull request #67 by iwiznia (2013-08-01 17:29:11+00:00)
Title: Added option 'position' to a column

This functionality is useful when you have a datagrid and want to have another datagrid with one more column, but added to a position other that last. like in this case:

```ruby
class Report
include Datagrid
scope do
SomeModel
end
column(:name)
column(:description)
end

class InheritedReport < Report
column(:id, :position => 1)
end
```

Without this option, it would be impossible to add the id column between the name and the description.
Note, that this does not if you try to position a column in a position thats not already defined. So this wouldn't work:

```ruby
class Report
include Datagrid
scope do
SomeModel
end
column(:name, :position => 1)
column(:description)
end
```

I could change the code a little bit to support that, if it's needed.