first version
Chart.js(Line Chart) adjust default options of Line Chart

set Default option: hitDetectionRadius to the same as radius, so when
there are many points there will only be one tooltip
the same adjust to Radar chart as previous commit
update test code, enable highlight feature
fix bug: tooltips clip issue

In Line Chart the most right tooltip always show partially due to no space
left. The solution is offset the caret under this condition.
adjust caret position properly
update README