Capitalize "Swap" and "Skipped" field labels

After the build completes, fade out the builders table in 2.5 seconds.
Nobody needs to see a table showing all the builders in "shutdown" mode.

A history.json file holds up to 500 log entries.  16 bytes of spaces were
removed which reduces the history file size by 8000 bytes.  Spaces were
also removed from summary.json which can account for 20%+ of the size.

The last history.json file was being written/rewritten every 3 seconds
regardless if there were changes to it or not.  Now it's only written
if it's changed since the previous write.  This might help reduce errors
seen by in nginx access log which are thought to occur when file changes
as the file is being served.