Doesn't install on node 0.8

[ljharb]

See https://travis-ci.org/ljharb/es7-shim/jobs/46043274 for failure output.

var tmpdir = require("os").tmpdir();
                           ^
TypeError: Object #<Object> has no method 'tmpdir'
    at Object.<anonymous> (/home/travis/build/ljharb/es7-shim/node_modules/runsync/index.js:11:28)
    at Module._compile (module.js:449:26)
    at Object.Module._extensions..js (module.js:467:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:362:17)
    at require (module.js:378:17)
    at Object.<anonymous> (/home/travis/build/ljharb/es7-shim/test/util/runner.js:1:74)
    at Module._compile (module.js:449:26)
    at Object.Module._extensions..js (module.js:467:10)

It'd be ideal if this module could be used on as many versions of node as possible. Is there any way that could happen, at least for node 0.8?