(travis) use v8 7.5

.travis.yml

@@ -5,11 +5,11 @@ services:
   - docker
 
 env:
-  - V8VER=7.1
+  - V8VER=7.5
     PHPVER=7.0
-  - V8VER=7.1
+  - V8VER=7.5
     PHPVER=7.1
-  - V8VER=7.1
+  - V8VER=7.5
     PHPVER=7.2
 
 script: make -f Makefile.travis test

Makefile.travis

@@ -1,5 +1,5 @@
 # Configure and build scripts for travis CI system
-V8VER ?= 7.1
+V8VER ?= 7.5
 
 IMAGENAME ?= v8js-test