Fix tox configuration.

-   Make sure tox-tmpl.ini and tox.ini are consistent

-   Avoid coverage 4.x

    Coverage 4.0a1 CLI is not happy with the commands we use in the unittests.
    Avoiding it for now.

Change-Id: I6976d4a94358692f5cb9570f672f6dd985f5d1b1
Minor documentation edits

Change-Id: I0f8049241ffd870a4dac405fa0ca53fb122f2181
Doc: status= -> status_code=

Change-Id: Ic4f32a8d1b96aea80b4c3032cdea6a608fe0bf81