unit test for making `step` respect linestyle as a kwarg
Changed `step` to append the user specified `linestyle` onto the
`linestyle` that is passed to `plot` instead of silently ignoring it.
pep8 fixes
variable name tweaks for readability
fixed random text insertion
fixed small issues with png test output, probably related to changes made in c48afe4b36112c58a45621c58c4a9f6f767f82c5
added CHANGELOG entry for this feature.
Merge pull request #1802 from tacaswell/step_linestyle

Step linestyle