Update minimum version to 4.63

The next release technically contains breaking changes - however, given that these
changes are required by 4.63, bumping the minimum version makes it seem reasonable
to do it as a minor update

Author: fredemmott

.travis.yml

@@ -2,7 +2,7 @@ sudo: required
 language: generic
 services: docker
 env:
-- HHVM_VERSION=4.60-latest
+- HHVM_VERSION=4.63-latest
 - HHVM_VERSION=latest
 - HHVM_VERSION=nightly
 install:

composer.json

@@ -4,7 +4,7 @@
   "license": "MIT",
   "keywords": ["hack", "TypeAssert"],
   "require": {
-    "hhvm": "^4.60",
+    "hhvm": "^4.63",
     "hhvm/hsl": "^4.0"
   },
   "extra": {