Use tox for lint.

README.md

@@ -26,9 +26,6 @@ conf layout.
 
 #. Test code base: `./venv/bin/tox`
 
-#. Check coding style for the whole project `./venv/bin/pylint letsencrypt`,
-   or specific module, e.g. `./venv/bin/pylint letsencrypt.client.acme`.
-
 ## Command line usage
 
 ```

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py26, py27
+envlist = py26, py27, lint
 
 [testenv]
 # install_command requires tox>=1.6
@@ -12,3 +12,6 @@ install_command = pip install --process-dependency-links {opts} {packages}
 commands = nosetests
 deps =
     nose
+
+[testenv:lint]
+commands = pylint letsencrypt