Upgrade to coverage 3.7.1 and have it auto-build itself on first use.

third_party/coverage-3.7.1/doc/contributing.rst

 .. _contributing:
 
 ===========================
 Contributing to coverage.py
 ===========================
 
 :history: 20121112T154100, brand new docs.
 
 .. highlight:: console
 
@@ skipping 86 matching lines @@
     py26 runtests: commands[6]
     === CPython 2.6.6 with C tracer (/home/ned/coverage/tox/py26/bin/python) ===
     ...........................................................................................(etc)
     ----------------------------------------------------------------------
     Ran 364 tests in 11.458s
 
     OK
     (and so on...)
 
 Tox runs the complete test suite twice for each version of Python you have
-installed.  The first run uses the Python implementation of the trace
-function, the second uses the C implementation.
+installed.  The first run uses the Python implementation of the trace function,
+the second uses the C implementation.
 
 To limit tox to just a few versions of Python, use the ``-e`` switch::
 
     $ tox -e py27,py33
 
 To run just a few tests, you can use nose test selector syntax::
 
-    $ tox test.test_misc:SetupPyTest.test_metadata
+    $ tox tests.test_misc:SetupPyTest.test_metadata
 
-This looks in `test/test_misc.py` to find the `SetupPyTest` class, and runs the
-`test_metadata` test method.
+This looks in `tests/test_misc.py` to find the `SetupPyTest` class, and runs
+the `test_metadata` test method.
 
 Of course, run all the tests on every version of Python you have, before
 submitting a change.
 
 
 Lint, etc
 ---------
 
 I try to keep the coverage.py as clean as possible.  I use pylint to alert me
 to possible problems::
 
     $ make lint
-    pylint --rcfile=.pylintrc coverage setup.py test
-    python -m tabnanny coverage setup.py test
+    pylint --rcfile=.pylintrc coverage setup.py tests
+    python -m tabnanny coverage setup.py tests
     python igor.py check_eol
 
 The source is pylint-clean, even if it's because there are pragmas quieting
 some warnings.  Please try to keep it that way, but don't let pylint warnings
 keep you from sending patches.  I can clean them up.
 
 
 Coverage testing coverage.py
 ----------------------------
 
@@ skipping 11 matching lines @@
 Contributing
 ------------
 
 When you are ready to contribute a change, any way you can get it to me is
 probably fine.  A pull request on Bitbucket is great, but a simple diff or
 patch is great too.
 
 
 .. _Mercurial: http://mercurial.selenic.com/
 .. _tox: http://tox.testrun.org/