Point Travis to python 3.5 and codecov.io

.travis.yml

 language: python
 python:
-    - "2.7"
+    - "3.5"
 sudo: false
 
 # Cache the pip directory. "cache: pip" doesn't work due to install override. See https://github.com/travis-ci/travis-ci/issues/3239.
@@ -11,7 +11,7 @@ before_install:
     - "export DISPLAY=:99.0"
     - "sh -e /etc/init.d/xvfb start"
 install:
-    - pip install -U pip wheel coveralls
+    - pip install -U pip wheel codecov
     - pip install -r requirements/test.txt
 script:
     - make validate
@@ -19,4 +19,4 @@ branches:
     only:
         - master
 after_success:
-    - coveralls
+    - codecov

README.rst

@@ -7,8 +7,8 @@ Course Discovery Service  |Travis|_ |Coveralls|_
 .. |Travis| image:: https://travis-ci.org/edx/course-discovery.svg?branch=master
 .. _Travis: https://travis-ci.org/edx/course-discovery
 
-.. |Coveralls| image:: https://coveralls.io/repos/edx/course-discovery/badge.svg?branch=master
-.. _Coveralls: https://coveralls.io/r/edx/course-discovery?branch=master
+.. |Codecov| image:: http://codecov.io/github/edx/course-discovery/coverage.svg?branch=master
+.. _Codecov: http://codecov.io/github/edx/course-discovery?branch=master
 
 The ``README.rst`` file should start with a brief description of the repository,
 which sets it in the context of other repositories under the ``edx``