fix data-table: fix cells paddings and add responsive behaviour

Before, there were no padding for TH and TD cells. There is now a 16px padding for TD and TH. Data tables have also a responsive behaviour.
chore demo: data-table demo updated with padding fix and responsive

Data-table demo has been updated with padding fix and responsive
behaviour.
Merge pull request #27 from lumapps/fix/data-table

Fix/data table: fix cells paddings and add responsive behaviour