Proposed changes

Inspired by the example stem plot.

1. Z order

Currently the stems are on top of the markers. This is in agreement with the MATLAB behavior http://de.mathworks.com/help/matlab/ref/stem.html#btrw_xi-94

However, it looks a bit untidy. I propose to place the markers on top.

2. Example coloring

The example cycles through the stem colors. IMO this is an untypical use case. The example (in particular if we just have one) should show a typical diagram. Therefore, we should change it to just one stem color.