Use log entry for status bar instead of a final graph

[schloerke]

Fixes #60

Do not read the current value from a graph that has processed all log entries

Instead read from the current log entry

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PR task list:

• [x] Passes devtools::check()
• [x] Add NEWS entry explaining change (reference username and PR#)
• [NA] Add tests (if appropriate)
• [NA] Update documentation with devtools::document()