Add coverage to tox, fixup buildout

.gitignore

@@ -1,5 +1,5 @@
 *.pyc
-.coverage
+.coverage*
 .installed.cfg
 .tox/
 __pycache__
@@ -8,5 +8,7 @@ develop-eggs
 include/
 lib/
 parts
+pip-selfcheck.json
+pyvenv.cfg
 share/
 src/*.egg-info

buildout.cfg

@@ -16,4 +16,4 @@ interpreter = py
 [test]
 recipe = zc.recipe.testrunner
 eggs = grokcore.message [test]
-defaults = ['--tests-pattern', '^f?tests$', '-v', '-c']
+defaults = ['-v', '-c']

tox.ini

@@ -1,16 +1,38 @@
 [tox]
 envlist =
+    coverage-clean,
     py27,
     py34,
     py35,
     py36,
     pypy,
-    pypy3
+    pypy3,
+    coverage-report
 
 [testenv]
 commands =
-    coverage run -m zope.testrunner --test-path=src {posargs:-vc}
+    coverage run --source=grokcore.message -m zope.testrunner --test-path=src {posargs:-vc}
+setenv =
+  COVERAGE_FILE=.coverage.{envname}
 deps =
     .[test]
     zope.testrunner
     coverage
+
+[testenv:coverage-clean]
+deps = coverage
+setenv =
+  COVERAGE_FILE=.coverage
+skip_install = true
+commands = coverage erase
+
+[testenv:coverage-report]
+deps = coverage
+setenv =
+  COVERAGE_FILE=.coverage
+skip_install = true
+commands =
+    coverage combine
+    coverage report
+    coverage html
+    coverage