separate environment to test codestyle as proposed by @sigmavirus24

tox.ini

@@ -3,7 +3,7 @@
 
 
 [tox]
-envlist = py26, py27, py35, pypy
+envlist = py26, py27, py35, pypy, codestyle
 
 
 [testenv]
@@ -20,3 +20,9 @@ commands =
         --verbose \
         --doctest-modules \
         {posargs:./httpie ./tests}
+
+[testenv:codestyle]
+deps = pycodestyle
+commands =
+    pycodestyle \
+        --ignore=E241,E501