Update module-level docstring for clarity.

Author: shawnbrown

pytest_datatest.py

@@ -2,29 +2,31 @@
 """
 A pytest plugin for test driven data-wrangling with datatest.
 
-This plugin is bundled with the ``datatest`` package however,
-it's developed separately as ``pytest_datatest``.
-
 IMPORTANT: Users of Datatest should only install ``datatest``
-itself, not this separate package. But developers of the Datatest
-project should install both ``datatest`` and ``pytest_datatest``.
-
-When both packages are installed, ``pytest_datatest`` is used
-in place of the bundled version.
-
-This is done for a few reasons:
-
-1. It's desirable for the plugin to follow the Pytest project's
-   plugin submission guidelines. Even if this plugin is never
-   submitted to the pytest-dev organisation, it's still good
-   practice to follow the guidelines used by official plugins.
-2. Datatest should work as expected out-of-the-box and the extra
-   code (a single script) is easy to bundle and it's so small
-   that there is no impact on user experience.
-3. Datatest supports more version of Python than does Pytest
-   or tox. It is helpful to keep the testing of the larger
-   datatest project separate from the testing of the pytest
-   plugin component.
+itself, not the ``pytest_datatest`` development package.
+
+This plugin is bundled with the datatest however, it's developed
+separately. This is done for a few reasons:
+
+1. Datatest should work as expected out-of-the-box. The plugin
+   code is small enough that including it does not impact the
+   user experience for non-pytest users. Offering the plugin as
+   an optional dependency would add a step to the installation
+   process for no real benefit.
+2. Following pytest's plugin submission guidelines seems like
+   good practice for long-term maintenance. But the guidelines
+   aren't easily implemented for datatest as a whole. Maintaining
+   the plugin in a separate repository makes it easier to follow
+   the guidelines without having to retool the main datatest
+   project.
+3. Datatest supports more versions of Python than does Pytest
+   or tox. The separate repository provides a clean separation
+   between the two sets of test requirements.
+
+Developers of the Datatest project should install both
+``datatest`` and ``pytest_datatest``. When both packages
+are installed, ``pytest_datatest`` is used in place of
+the bundled version.
 """
 
 import re