Adding coverage generation to tox (pallets#2071)

* Adding coverage generation to tox

* Removing test directory from coverage command

* Adding back  to pytest command

Author: Alex Kahan

.gitignore

@@ -11,3 +11,9 @@ _mailinglist
 .tox
 .cache/
 .idea/
+
+# Coverage reports
+htmlcov
+.coverage
+.coverage.*
+*,cover

tox.ini

@@ -4,11 +4,12 @@ envlist = {py26,py27,pypy}-{lowest,release,devel}{,-simplejson}, {py33,py34,py35
 
 
 [testenv]
+usedevelop=true
 commands =
-    py.test []
-
+    py.test [] --cov=flask --cov-report html
 deps=
     pytest
+    pytest-cov
     greenlet
 
     lowest: Werkzeug==0.7