Re-Drawing charts on resize, avoids charts going beyond viewport.

Hello Keen,

**Feature** : [issue #61](https://github.com/keen/dashboards/issues/61)
Redrawing charts on resize to avoid the charts to spanning beyond the viewport.

Has only been done in one example so far, but the `resize` function can be moved to a global js file, so that all charts are redrawn. 

When the `drawCharts()` function is moved up a level of scope and invoked by the `Keen.ready()` function it fires an error
###### Uncaught TypeError: Cannot read property 'apply' of undefined  (keen.min.js)
This is something I haven't been able to figure out and would like to know what it's expecting.


*It's my first fork, I'll be more than happy to fix any errors if they arise* : ]
Cheers!