Fixed tooltip. Removed points where no data available.
Fixed tooltip. Removed points where no data available.

Tooltip code inspired by: bl.ocks.org/weiglemc/6185069

CSE512-16S/a3-janetmatsen-mdmurbach,JanetMatsen/CSE_512_A3,CSE512-16S/a3-janetmatsen-mdmurbach