Add tox as test runner + update Travis configuration.

The new test runner is needed as Travis does not know `python2` and `python3`.
(BTW I have the same problem on my computer, so I cannot use the previous
approach with the Makefile without modifications on my system.)

The tests in grammar/test_grammar.py are not run because I was not able to find
out how to run `make` in the `grammar` directory before installing the package.

See https://tox.readthedocs.io for documentation on tox and
https://docs.pytest.org for documentation on pytest. (These tools are widely
used in the Python community and would make it easier for contributors to run
the tests.)

I had to fix two tests to be able to run them successfully.

.gitignore

@@ -1,2 +1,5 @@
 build/
 *.pyc
+.tox/
+.cache/
+*.egg-info/

.travis.yml

@@ -1 +1,11 @@
 language: python
+python:
+    - 2.7
+    - 3.3
+    - 3.4
+    - 3.5
+    - 3.6
+install:
+    - pip install tox-travis
+script:
+    - tox

HOWTODIST

@@ -11,7 +11,13 @@ $ cd odfpy
 
 Run the automated tests:
 
-$ cd tests ; make ; cd ..
+Install `tox` via `pip` when running the tests for the first time:
+
+$ pip install tox
+
+Run the tests for all supported python versions:
+
+$ tox
 
 Remove the "dev" marker from the version in setup.py and odf/namespaces.py
 

setup.cfg

@@ -0,0 +1,7 @@
+[bdist_wheel]
+universal=1
+
+[tool:pytest]
+norecursedirs = grammar
+addopts = tests
+python_files = test*.py

tests/teststyles.py

@@ -88,8 +88,8 @@ def testAttributeForeign(self):
         textdoc.styles.addElement(standard)
         s = textdoc.stylesxml()
         s.index(u"""<?xml version='1.0' encoding='UTF-8'?>\n""")
-        s.index(u'xmlns:ns41="http://foreignuri.com"')
-        s.index(u'<style:paragraph-properties ns41:enable-numbering="true"/>')
+        s.index(u'xmlns:ns44="http://foreignuri.com"')
+        s.index(u'<style:paragraph-properties ns44:enable-numbering="true"/>')
         e = ElementParser(s,u'style:style')
 #        e = ElementParser('<style:style style:name="Standard" style:display-name="Standard" style:family="paragraph">')
         self.assertEqual(e.element,u'style:style')

tests/testunicode.py

@@ -40,6 +40,8 @@ def assertContains(self, stack, needle):
     def assertNotContains(self, stack, needle):
         self.assertEqual(-1, stack.find(needle))
 
+    @unittest.skipIf(sys.version_info[0] != 2,
+                     "For Python3, unicode strings are type 'str'.")
     def test_xstyle(self):
         self.assertRaises(UnicodeDecodeError, style.Style, name="X✗", family="paragraph")
         xstyle = style.Style(name=u"X✗", family=u"paragraph")

tox.ini

@@ -0,0 +1,13 @@
+[tox]
+envlist =
+    py27,
+    py33,
+    py34,
+    py35,
+    py36,
+
+[testenv]
+commands =
+    pytest
+deps =
+    pytest