Fallback to os temp directory if findCacheDir fail

From the readme: `Finds the cache dir using the supplied options. The algorithm tries to find a package.json file, searching every parent directory of the cwd specified (or implied from other options). It returns a string containing the absolute path to the cache directory, or null if package.json was never found.` This is a fallback for null condition. Investigated after @gaearon comments on facebook/create-react-app#1578 (comment)

index.js

@@ -5,6 +5,7 @@ var crypto = require("crypto")
 var fs = require("fs")
 var findCacheDir = require("find-cache-dir")
 var objectHash = require("object-hash")
+var os = require("os")
 
 var engines = {}
 var cache = null
@@ -165,7 +166,7 @@ module.exports = function(input, map) {
         thunk: true,
         create: true,
       })
-      cachePath = thunk("data.json")
+      cachePath = thunk("data.json") || os.tmpdir() + '/data.json';
       try {
         cache = require(cachePath)
       }