removed xlab and ylab, use x_title and y_title instead. Added rotate_x_title and rotate_x_labels
added x_jitter and y_jitter to points (removed plain jitter)
x_lab to x_title, xlim to x_lim (same for y)
removed color_group size check in points, added test to show that color_groups can be smaller than num_points
(as long as it's a multiple)
fixed the behavior of hide,  added padding to tooltip
renamed file to file_name
titles no longer need to be shown (use title = "" to remove them)
fix bottom margin
helpful comments
simplified get_categories and get_data_ranges
fixed color bug in lines
fixed lines tooltip bug
set an explicit domain to the color_scale, fixed palette bugs
jitter should be different in x and y
fixed scale domain
fixed named palette bug in points
Allow formatting axes labels Closes #43

The syntax is clickme(1:1000, x_format = "s", y_format = ".2f"). Format specification in https://github.com/mbostock/d3/wiki/Formatting#d3_format
Changed clipping path size
fixed bug when calling clickme without specifying template
Axes titles are now hidden when not specified