Make tox work against 2.7 and 3.4 for quick check

Travis can then check more versions and catch any lingering problems,
but this at least allows one Python 2 and one Python 3 spot-check
locally before issuing a commit.

Author: brandon-rhodes

tox.ini

@@ -1,8 +1,16 @@
 [tox]
-envlist = py26, py27
+envlist = py27, py34
 [testenv]
 commands = python -m unittest discover ephem
-[testenv:py26]
-deps =
-    unittest2
-commands = unit2 discover ephem
+
+# Without the following "basepython" directives, tox will try building a
+# virtual environment using the Anaconda version of Python on my path,
+# and then platform.python_version() inside of its virtual environment
+# dies with "ValueError: failed to parse CPython sys.version".
+
+[testenv:py27]
+changedir = .tox
+basepython = /usr/bin/python2.7
+[testenv:py34]
+changedir = .tox
+basepython = /usr/bin/python3.4