Merge pull request #92 from Balrog30/gh-pages

Merge multiple commits from Balrog30/angular-google-chart.
Do not create new chartWrapper every time.

Creating new chartWrapper on every update causes major memory leaks, that are a real problem if you update graphs every second.

Signed-off-by: matematik7 <domen.ipavec@z-v.si>
Keep ChartWrapper but update user-changeable properties if chartWrapper exists.