Update 7.4 version

Seems Travis doesn't support 7.4 yet

Author: shabbyrobe

.travis.yml

@@ -12,13 +12,12 @@ matrix:
   include:
     - { dist: trusty , php: "hhvm-3.3" }
     - { dist: trusty , php: "hhvm-3.6" }
-    - { dist: trusty , php: "hhvm-3.6" }
+    - { dist: trusty , php: "hhvm-3.9" }
     - { dist: trusty , php: "hhvm-3.12" }
     - { dist: trusty , php: "hhvm-3.15" }
     - { dist: trusty , php: "hhvm-3.18" }
-    - { dist: trusty , php: "hhvm-nightly" }
     - { dist: trusty , php: "nightly" }
-    - { dist: trusty , php: "7.4" }
+    - { dist: trusty , php: "7.4snapshot" }
     - { dist: trusty , php: "7.3" }
     - { dist: trusty , php: "7.2" }
     - { dist: trusty , php: "7.1" }
@@ -30,7 +29,6 @@ matrix:
 
   allow_failures:
     - php: "nightly"
-    - php: "hhvm-nightly"
 
 branches:
   only: