Enable Selecting a single bar on the timeline

[Rperry2174]

This is closely related to #99 , but splitting this out to make that issue simpler -- also related to #621

Added functionality

Goal: Be able to click on distinct yellow bars to render the profile for that specific timestamp

We've had some request that from a UX perspective it would be ideal to also be able to "click" on a yellow bar as opposed to having to drag from before and after in order.

Basically there are some situations where the timeline is so long, that yellow bars are not distinct from each other. In these situations this functionality would not be available and one would drag to "zoom" in on a time period as usual:
6 months of data (each bar is 10s so you can't select an individual bar here)

However in other situations when you are looking at a more granular time range, one could and should be able to click on a specific yellow bar and have that flamegraph rendered:

15 minutes of data (each bar is 10s so you can select an individual bar here)

For situations like these <15minutes, we should:

1. Make the width of the bars a little bit wider
2. When a bar is "hovered" over it should go into a hover state that indicates visually that the yellow bar can be "clicked" on