Document available steps about behave-test-steps HOT 2 OPEN

Also, from #5, the following environment variables should be documented:

• MAVEN_MIRROR_URL
• BEHAVE_TIMEOUT

from behave-test-steps.

--steps-catalog might help. E.g.

$ behave --dry-run --format=steps.catalog | head
Given define variable
  Location: steps/steps.py:294

Given container is started with env
  Location: steps/container_steps.py:72

Given container is started with args
  Location: steps/container_steps.py:86

Given container is started with entrypoint {entrypoint}

Possibly useful formatters (shown by --format=help are)

• steps: groups Given/when/then which is useful, links to implementation path:line; doesn't include docs
• steps.catalog: groups given/when/then; reports implementation path:line on an indented second line; includes docs when the steps have them;
• steps.usage: reports on the usage of steps for a particular image. THus not generically useful

The output of steps.catalog could be lightly marked up and turned into HTML, perhaps pushd to github pages on commit.

PoC here: https://github.com/jmtd/behave-test-steps/tree/gh-pages-doc-steps ; example output: https://github.com/jmtd/behave-test-steps/blob/gh-pages-doc-steps/docs.md

from behave-test-steps.