Fix "incomplete" test fixture to be valid gzip of incomplete data (#167)

The zlib module in Node 5 now throws if it sees an unexpected end of
file, so the current test that the tilelive decode correctly throws
on incomplete JSON currently fails because the unzip part of the
pipeline is throwing instead.

.travis.yml

@@ -4,6 +4,7 @@ node_js:
  - "0.10"
  - "0.12"
  - "4"
+ - "5"
 
 script:
  - npm test

package.json

@@ -51,7 +51,7 @@
     "tilelive-copy": "./bin/tilelive-copy"
   },
   "engines": {
-    "node": ">= 0.10.0 < 5"
+    "node": ">= 0.10.0"
   },
   "scripts": {
     "test": "eslint --no-eslintrc -c .eslintrc lib/*.js && tape test/*.test.js",