styled nvd3 charts

- Rounded Tooltips
- Changed tooltip header color to green
- Changed tooltip font size
- Changed color of x and y axis and labels to white
- Increased height of charts in JS and CSS so charts don't look squished

==== Employee Chart
- Removed tick lines inside discrete bar chart
- Rotated X-axis labels
- Changed color of discrete bar chart bars

==== Pie Chart
- Changed color of pie chart bars
- Repositioned legend for pie chart

==== Crime Chart
- Removed option to stack results because it was looking janky
- Changed colors of bars in crime chart


@drewrwilson @boonrs 

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