Retro delta always b/w; no delta if bg = '---'
No delta for CGM errors
fixed #283 by changing  to
Merge pull request #277 from jimsiff/wip/bgDelta

Delta BG minor fixes
got rid of the toolbar hide/show feature since it wasn't used
Merge pull request #284 from nightscout/wip/no-hiding

Remove the toolbar hide/show feature since it wasn't used
Merge pull request #14 from nightscout/dev

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