MAINT: enable cron switch

* now that anaconda.org upload has
been observed in the absence of a cron
requirement in PR 69, go ahead &
restore the cron requirement

Author: tylerjereddy

.travis.yml

@@ -140,7 +140,7 @@ after_success:
     # SCIPY_WHEELS_NIGHTLY is a secret token
     # used in Travis CI config, originally
     # generated at anaconda.org for scipy-wheels-nightly
-    - if [ "$TRAVIS_EVENT_TYPE" != "cron" ]; then
+    - if [ "$TRAVIS_EVENT_TYPE" == "cron" ]; then
           ANACONDA_ORG="scipy-wheels-nightly";
           conda create -q -n test-environment python=${MB_PYTHON_VERSION} anaconda-client;
           conda activate test-environment;