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

third_party/coverage-3.7.1/doc/contributing.rst

Index: third_party/coverage-3.7.1/doc/contributing.rst
diff --git a/third_party/coverage-3.6/doc/contributing.rst b/third_party/coverage-3.7.1/doc/contributing.rst
similarity index 94%
rename from third_party/coverage-3.6/doc/contributing.rst
rename to third_party/coverage-3.7.1/doc/contributing.rst
index 90b9ba1bafb3b1563dd6951be929c25689c45342..88c99a99fcdc5069854a6cf71a99c815a8efecc4 100644
--- a/third_party/coverage-3.6/doc/contributing.rst
+++ b/third_party/coverage-3.7.1/doc/contributing.rst
@@ -104,8 +104,8 @@ The tests are written as standard unittest-style tests, and are run with
     (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::
 
@@ -113,10 +113,10 @@ To limit tox to just a few versions of Python, use the ``-e`` switch::
 
 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.
@@ -129,8 +129,8 @@ 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