printLevelVertical only prints double bars, never single bars

[tofof]

The logic for printing single bars is erroneous; the condition will always be false when that code is reached (>=0 has to be false already, so obviously >=1 will be false).

This can be easily verified using the FunPrintLevel example and changing the step size to 1, along with a Serial.print of the current level. The first bar should draw at 13, but no bars appear until a double bar at 25, and then another double bar at 50, etc.

Fixed by included PR #58.