Require HHVM 4.13+

Supporting 4.14 requires replacing instanceof with is; 4.13 contains
performance improvements to `is` expressions making this change
practical outside of repo-authoritative mode.

Author: fredemmott

.travis.yml

@@ -2,8 +2,7 @@ sudo: required
 language: generic
 services: docker
 env:
-- HHVM_VERSION=4.1-latest
-- HHVM_VERSION=4.2-latest
+- HHVM_VERSION=4.13-latest
 - HHVM_VERSION=latest
 - HHVM_VERSION=nightly
 install:

composer.json

@@ -5,7 +5,7 @@
     "homepage": "https://github.com/facebook/xhp-lib",
     "license": ["MIT"],
     "require": {
-        "hhvm": "^4.0.0",
+        "hhvm": "^4.13.0",
         "hhvm/type-assert": "^3.0"
     },
     "require-dev": {