Added tox.ini file

Signed-off-by: Grzegorz Latosinski <glatosinski@antmicro.com>

tox.ini

diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..0979f90
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,27 @@
+[tox]
+envlist = py{27,34,35,36,37}
+
+[testenv]
+setenv =
+    PYTHONPATH={toxinidir}/vtr_xml_utils
+basepython =
+    py35: python3.5
+    py36: python3.6
+    py37: python3.7
+deps =
+    check-manifest
+    # If your project uses README.rst, uncomment the following:
+    # readme_renderer
+    flake8
+    pytest
+    lxml
+commands =
+    check-manifest --ignore tox.ini,tests*
+    # This repository uses a Markdown long_description, so the -r flag to
+    # `setup.py check` is not needed. If your project contains a README.rst,
+    # use `python setup.py check -m -r -s` instead.
+    python setup.py check -m -s
+    flake8 .
+[flake8]
+exclude = .tox,*.egg,build,data
+select = E,W,F