Support keyword lists

[Wojtek Mach]

Basically supporting this:

Tabula.print_table([[foo: 1, bar: 2], [foo: 3, bar: 4]])

The advantage of being able to use keywords is that they keep order. Currently to have it in particular order on a list of maps, we'd need to repeat field names: only: [:foo, :bar]

[hq1]

Closed via fusillicode@b841e16