Steemconnect (v3) Bugfix

Pull request:
https://github.com/steemscript/steemconnect.js/pull/68

I was working on a node.js backend when I ran into the following issue with the comment and vote function of Steemconnect:

window is not defined                                                                                                                                          21:37:25

  at hasChromeExtension (node_modules/steemconnect/lib/index.js:43:3)
  at useSteemKeychain (node_modules/steemconnect/lib/index.js:49:11)
  at Client.vote (node_modules/steemconnect/lib/index.js:201:11)
  at steemconnectClient.me (api/index.js:104:34)
  at node_modules/steemconnect/lib/index.js:179:16
  at process._tickCallback (internal/process/next_tick.js:68:7)

I thought window && ... should be fine but apparently it was not. This lead me to the solution:
https://stackoverflow.com/questions/4186906/check-if-object-exists-in-javascript

So now Steemconnect (3.0.1) works with Node.js as intended: SteemConnect.js was designed to work both in the browser and in Node.js.

Thank you @fabien for taking action so quickly and releasing a new version. I can continue with my project now, which will be announced soon. :)