Add a pathExpression to constantLine
Merge pull request #897 from markolson/give-constantline-a-pathExpression-0.9.x

Add a pathExpression to constantLine
clarifiying areaBetweens arg expectation, & how to use the  function with it
removing a trailing space
Merge pull request #900 from gwaldo/0.9.x

Describe use of 'group' to have multiple values in areaBetween to 0.9.x branch