Merge pull request #2015 from blink1073/codecov

MAINT: Switch from coveralls -> codecov in CI build

.travis.yml

@@ -62,5 +62,5 @@ install:
 script: tools/travis_script.sh
 
 after_success:
-    - coveralls
+    - codecov
     - bash tools/deploy_docs.sh

tools/travis_before_install.sh

@@ -48,7 +48,7 @@ virtualenv -p python ~/venv
 source ~/venv/bin/activate
 
 pip install --upgrade pip
-pip install --retries 3 -q wheel flake8 coveralls nose
+pip install --retries 3 -q wheel flake8 codecov nose
 
 # install wheels
 for requirement in $WHEELBINARIES; do