Adds php-nightly to test matrix

- Future 7.3

Author: weierophinney

.travis.yml

@@ -33,6 +33,9 @@ matrix:
     - php: 7.2
       env:
         - DEPS=latest
+    - php: nightly
+      env:
+        - DEPS=latest
 
 before_install:
   - if [[ $TEST_COVERAGE != 'true' ]]; then phpenv config-rm xdebug.ini || return 0 ; fi