Add missing packages from setup.py, add tox config.

Add missing `requests` and `warcio` packages. They are used in unit tests but
they were not included in `setup.py`.

Add `tox` configuration in order to be able to run unit tests for py27,
py34 and py35 with 1 command.

setup.py

@@ -41,6 +41,8 @@ deps = [
     'urlcanon>=0.1.dev16',
     'doublethink>=0.2.0.dev81',
     'PySocks',
+    'warcio',
+    'requests'
 ]
 try:
     import concurrent.futures

tox.ini

@@ -0,0 +1,9 @@
+[tox]
+envlist=py27,py34,py35
+[testenv]
+deps=
+  pytest
+  pytest-xdist
+  requests
+  mock
+commands=py.test -n 4