Improve tooltip for bucket UI

Reconstructed the tooltip with bootstrap stuff
to give more detailed informations about each
chunks

Signed-off-by: Geoffrey Beausire <g.beausire@criteo.com>

CHANGELOG.md

@@ -34,6 +34,7 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 
 - [#1933](https://github.com/thanos-io/thanos/pull/1933) Add a flag `--tsdb.wal-compression` to configure whether to enable tsdb wal compression in ruler and receiver.
 - [#2021](https://github.com/thanos-io/thanos/pull/2021) Rename metric `thanos_query_duplicated_store_address` to `thanos_query_duplicated_store_addresses_total` and `thanos_rule_duplicated_query_address` to `thanos_rule_duplicated_query_addresses_total`.
+- [#2166](https://github.com/thanos-io/thanos/pull/2166) Improve tooltip for bucket web UI.
 
 ## [v0.10.1](https://github.com/thanos-io/thanos/releases/tag/v0.10.1) - 2020.01.24