Add a tox configuration

.hgignore

 test/data/database
+.tox
+cubicweb_postgis.egg-info

tox.ini

+[tox]
+envlist = py27, flake8
+
+[testenv]
+sitepackages = True
+deps =
+  pytest
+commands =
+  {envpython} -m pytest {posargs}
+
+[testenv:flake8]
+skip_install = true
+whitelist_externals =
+  flake8
+deps =
+  flake8
+commands = flake8
+
+[flake8]
+exclude = migration/*,setup.py,.tox/*
+max-line-length = 100
+
+[pytest]
+python_files = *test_*.py