Vaadin 7 not supported

[HermanBovens]

Vaadin 7 is not supported (yet) by Invient Charts.
Now that Vaadin 7 alpha 3 is out, more and more people will want to start using it.

[michaeljfazio]

Converted the entire project to maven project in the following pull request: #4

Hopefully that makes the process of making InvientCharts Vaadin7 compliant a bit easier.