Fix tox.ini

Prior to this patch, test for Python 3.2 failed.

Also, arguments can be passed to iptest via tox command now.
e.g.: `tox -- IPython.core`

tox.ini

@@ -1,19 +1,26 b''
 # Tox (http://tox.testrun.org/) is a tool for running tests
 # in multiple virtualenvs. This configuration file will run the
 # test suite on all supported python versions. To use it, "pip install tox"
 # and then run "tox" from this directory.
 
 [tox]
 envlist = py26, py27, py32
 
 [testenv]
+deps =
+    nose
+
+# To avoid loading IPython module in the current directory, change
+# current directory to ".tox/py*/tmp" before running test.
+changedir = {envtmpdir}
+
 commands =
-    pip install -q --use-mirrors nose
+    # As pip does not treat egg, use easy_install to install PyZMQ.
+    # See also: https://github.com/zeromq/pyzmq
     easy_install -q pyzmq
-    iptest -w /tmp
+    iptest []
 
 [testenv:py32]
 commands =
-    pip install -q --use-mirrors nose
     easy_install -q pyzmq
-    iptest3 -w /tmp
+    iptest3 []