toxing for easy multiversion tests

.travis.yml

@@ -6,6 +6,6 @@ python:
   - "3.6"
   - "pypy"  # PyPy2 5.8.0
   - "pypy3" # Pypy3 5.8.0-beta0
+install: pip install tox-travis
 script:
-  - pip install -r nearley-requirements.txt
-  - python -m tests
+  - tox

tox.ini

@@ -0,0 +1,30 @@
+[tox]
+envlist = py27, py34, py35, py36, pypy, pypy3
+skip_missing_interpreters=true
+
+[travis]
+2.7 = py27
+3.4 = py34
+3.5 = py35
+3.6 = py36
+pypy = pypy
+pypy3 = pypy3
+
+# Note : We can depend on travis matrix if needed
+;[travis:env]
+;DJANGO =
+;  1.7: django17
+;  1.8: django18, docs
+
+[testenv]
+whitelist_externals = git
+deps =
+    -rnearley-requirements.txt
+
+# to always force recreation and avoid unexpected side effects
+recreate=True
+
+commands=
+    git submodule sync -q
+    git submodule update --init
+    python -m tests