Example documentation for Google Charts and Highcharts

Hi - thanks for this great tool! Integrated it into a site recently and it's working great. However, there is one thing that could have saved me a lot of time which is that, having had little experience with charting libs in general, I could really have done with seeing a few dirt simple examples of how to format the charts, and also where I could go to find all the rest of the customisation options for each lib. Therefore, in this pull request I've added a couple of examples to the README page and added links to the relevant APIs that that I feel can  provide the basic info that a charting newbie needs! If you think it's useful them feel free to merge in. Thanks.