Crashes when there is no internet connection

[siddharthkp]

Originally reported in #12

version 1.2.4 crashes when trying to request something without a network connection - I guess when it tries to verify if it's a trusted package or not.

/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/node_modules/sync-request/index.js:37
    throw new Error(response.error.message || response.error || response);
    ^

Error: getaddrinfo ENOTFOUND api.npmjs.org api.npmjs.org:443
    at doRequest (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/node_modules/sync-request/index.js:37:11)
    at isModulePopular (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/helpers.js:187:18)
    at Object.installModule (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/helpers.js:47:24)
    at FSWatcher.main (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/index.js:25:66)
    at emitOne (events.js:96:13)
    at FSWatcher.emit (events.js:188:7)
    at FSWatcher.<anonymous> (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/node_modules/chokidar/index.js:191:15)
    at FSWatcher._emit (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/node_modules/chokidar/index.js:233:5)
    at FSWatcher.<anonymous> (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/node_modules/chokidar/lib/fsevents-handler.js:204:14)
    at addOrChange (/Users/bananas/.nvm/versions/node/v6.2.2/lib/node_modules/auto-install/node_modules/chokidar/lib/fsevents-handler.js:210:7)