added <meta charset = 'utf-8'> to rChart.html template

Since d3.v3 requires utf-8, rCharts standalone would not work correctly with d3.v3.  This has not been a problem since most of the libraries still are using d3.v2.  As these upgrade though, this will be an issue.  As far as I know, there should not be in disadvantages to changing to utf-8.