Run check-manifset and readme_render with tox (#358)

Run these checks as part of the lint process to validate MANIFEST.in and
to make sure the long_description is correct.

.travis.yml

@@ -5,7 +5,7 @@ matrix:
     - python: 2.7
       env: TOXENV=py27
     - python: 2.7
-      env: TOXENV=pep8
+      env: TOXENV=lint
     - python: 3.4
       env: TOXENV=py34
     - python: 3.5

AUTHORS

@@ -19,3 +19,4 @@ Anna Martelli Ravenscroft <annaraven@gmail.com>
 Sumana Harihareswara <sh@changeset.nyc>
 Dustin Ingram <di@di.codes> (https://di.codes)
 Jesse Jarzynka <jesse@jessejoe.com> (http://jessejoe.com)
+László Kiss Kollár <kiss.kollar.laszlo@gmail.com>

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,pypy,py33,py34,py35,py36,docs,pep8
+envlist = py27,pypy,py33,py34,py35,py36,docs,lint
 
 [testenv]
 deps =
@@ -28,7 +28,14 @@ commands =
     python setup.py -q bdist_wheel sdist
     twine upload --skip-existing dist/*
 
-[testenv:pep8]
+[testenv:lint]
 basepython = python2.7
-deps = flake8
-commands = flake8 twine/ tests/ docs/
+deps =
+    flake8
+    check-manifest
+    readme_renderer
+commands =
+    flake8 twine/ tests/ docs/
+    -check-manifest -v
+    python setup.py check -r -s
+