Suggestion for a more responsive grid

The grid can now be used responsively with different column widths for
different devices (similar to Bootstrap). If not specified differently, larger solutions inherit the columns of the next smaller one

Notation:
*number* *screen* wide

Screens:
- mobile
- tablet
- computer
- large screen
- widescreen

Example:
```
<div class="sixteen wide mobile eight wide tablet four wide computer column two wide large screen one wide widescreen"></div>
```