Stop Travis from force pushing

We've lost a couple of merges in the past, let's not do that anymore.

.travis/push.sh

@@ -26,7 +26,7 @@ upload_files() {
   if [ $TRAVIS_EVENT_TYPE != "pull_request" ]; then
     if [ $TRAVIS_BRANCH == "master" ]; then
       echo "Pushing to master branch..."
-      git push --force --quiet "https://${GH_TOKEN}@github.com/30-seconds/30-seconds-of-code.git" master > /dev/null 2>&1
+      git push --quiet "https://${GH_TOKEN}@github.com/30-seconds/30-seconds-of-code.git" master > /dev/null 2>&1
     fi
   fi
 }