Update drawing of pie chart when there are single or no values

[sethfair]

• When the length of data is 1, it draws a path instead of a circle so hover functionality to use this.sector will work the same as if there are multiple slices. (line 85 - 102)
• Fix drawing when a single value equals the total. Prior, it did not draw the chart. This change draws a circle path. (line 134, 147-162)
• Added an additional option to ignore the min percentage and show all values. Passing in a min-percent as 0 to show all values and evaluating Boolean( minPercent ) is still false, so it didn’t show all values. Passing in in opts.ignoreMinPercent allows you to evaluate it correctly. (line 61)