Enabled coveralls again for Travis push events

Details:

* The previous commit ran coveralls only for "pull_request" Travis event
  types in order to create only the PR comments linking to the result.
  However, for reasons not yet understood, the PR comments are not always
  created. The "push" Travis event at least creates a result link in the
  section on checks, but it sometimes does not show the delta.

  At this point, it seems most sensible to run coveralls on both event
  types.

Signed-off-by: Andreas Maier <andreas.r.maier@gmx.de>

.travis.yml

@@ -235,10 +235,6 @@ after_success:
 #       make sure this project is enabled there.
 # Make sure the Python version matches the one specified for python-coveralls
 # in dev-requirements.txt.
-# On TRAVIS_EVENT_TYPE values: "pull_request" is important because it compares
-# the branch to its merge target. It creates/updates a single comment with the
-# results. "push" seems to compare to previous pushes and thus not always has
-# a reasonable result.
-  - if [[ "$TRAVIS_EVENT_TYPE" == "pull_request" && "$TRAVIS_OS_NAME" == "linux" && "$TRAVIS_PYTHON_VERSION" == "3.4" && "$PACKAGE_LEVEL" == "latest" && -z $_MANUAL_CI_RUN ]]; then
+  - if [[ "$TRAVIS_OS_NAME" == "linux" && "$TRAVIS_PYTHON_VERSION" == "3.4" && "$PACKAGE_LEVEL" == "latest" && -z $_MANUAL_CI_RUN ]]; then
       coveralls;
     fi