Update to the way tox.ini looks like in other ZF packages.

This allows to run the in Python >= 3.5 again.

.gitignore

@@ -16,3 +16,4 @@ eggs/
 coverage.xml
 .tox
 nosetests.xml
+htmlcov/

tox.ini

@@ -1,19 +1,27 @@
 [tox]
 envlist =
-    py27,py34,py35,py36,pypy,pypy3,coverage
+    py27,py34,py35,py36,pypy,pypy3,coverage-report
 
 [testenv]
+usedevelop = True
 commands =
-    zope-testrunner --test-path={envsitepackagesdir} -s zExceptions
+    coverage run {envbindir}/zope-testrunner --path=src --all {posargs:-vc}
 deps =
+    .
     zope.testrunner
+    coverage
+setenv =
+    COVERAGE_FILE=.coverage.{envname}
 
-[testenv:coverage]
-basepython =
-    python2.7
+[testenv:coverage-report]
+basepython = python2.7
+deps = coverage
+setenv =
+    COVERAGE_FILE=.coverage
+skip_install = true
 commands =
-    nosetests --with-xunit --with-xcoverage --where={envsitepackagesdir}/zExceptions --cover-package=zExceptions
-deps =
-    nose
-    coverage
-    nosexcover
+    coverage erase
+    coverage combine
+    coverage html -i
+    coverage xml -i
+    coverage report -i