Try disabling coverage on master to prevent Travis crashes

We suspect that memory overhead caused by coverage might be the reason Travis fails on master. No guarantees it will work but worth a try.

Author: gaearon

.travis.yml

@@ -66,13 +66,7 @@ script:
           $SERVER
       fi
     elif [ "$TEST_TYPE" = test ]; then
-      if [ "$TRAVIS_PULL_REQUEST" = false ]; then
-        set -e
-        ./node_modules/.bin/grunt jest:coverage
-        cat ./coverage/lcov.info | ./node_modules/.bin/coveralls
-      else
-        ./node_modules/.bin/grunt jest:normal
-      fi
+      ./node_modules/.bin/grunt jest:normal
       echo 'Testing in server-render (HTML generation) mode...'
       printf '\nmodule.exports.useCreateElement = false;\n' \
         >> src/renderers/dom/shared/ReactDOMFeatureFlags.js