add tox configuration file

From the project webpage:

"""
Tox is a generic virtualenv management and test command line tool you can use
for:

- checking your package installs correctly with different Python versions and
  interpreters
- running your tests in each of the environments, configuring your test tool of
  choice
- acting as a frontend to Continuous Integration servers, greatly reducing
  boilerplate and merging CI and shell-based testing.
"""

.gitignore

@@ -9,3 +9,4 @@ libqpol/policy_scan.c
 setools/policyrep/qpol_wrap.c
 setools/policyrep/qpol.py
 *.so
+/.tox

tox.ini

@@ -0,0 +1,27 @@
+[tox]
+envlist     = py27, py33, py34
+
+[testenv:pep8]
+deps        = pep8
+commands    = pep8 setools/ setools/policyrep/ tests/ \
+                   seinfo seinfoflow sedta sesearch \
+                   --exclude qpol.py --statistics --max-line-length=100
+
+[testenv:coverage]
+deps        = networkx==1.9
+              coverage
+commands    = coverage erase
+              coverage run setup.py test
+              coverage report
+
+[testenv:coverage-html]
+deps        = networkx==1.9
+              coverage
+commands    = coverage erase
+              coverage run setup.py test
+              coverage report
+              coverage html
+
+[testenv]
+deps        = networkx==1.9
+commands    = {envpython} setup.py test