Merge pull request holman#54 from agordon/feature/min_max

Support SPARK_MIN/SPARK_MAX env variables.

Author: holman

spark

@@ -55,6 +55,9 @@ spark()
     numbers=$numbers${numbers:+ }$n
   done
 
+  [ -n "$SPARK_MIN" ] && min=$SPARK_MIN
+  [ -n "$SPARK_MAX" ] && max=$SPARK_MAX
+
   # print ticks
   local ticks=(▁ ▂ ▃ ▄ ▅ ▆ ▇ █)