Improved Mobile Browser Support & Added Flex() Feature

I have gone back and forth with one of the BlackBerry 10 Browser developers because there has been a large bug that breaks the grid layout as can be seen here:

[Mobile Browser Support](http://i.imgur.com/QJOCBvB.jpg)

I then found out that the exact same bug happens on iOS when using Safari OR Chrome. At this point, I knew it needed to be fixed.

[Received a response from the Browser Developer](https://twitter.com/kpiascik/status/544561841192849408)

And upon making a slight change to the code by adding a `flex-basis:` class, it fixed the support on iOS Safari/Chrome & BlackBerry 10

And now here's the new feature. By having a max & min width when using `block()` you entirely lose one of the cool feature of flex which allows it to just scale a new row to fill the entire width of the screen. So I have added an additional flex() feature which allows for that support and it acts identical to how block() works, it just allows the user more control whether they want it to flex to the the entire width or if they just want it to act as a block.

[Codepen showing new feature](http://codepen.io/Flip4Bytes/pen/gbrJaz)