createReadStream buffer support

[MrHen]

I opened a PR to add .createReadStream support: #50

The basic functionality is:

    awsMock.mock('S3', 'getObject', new Buffer('body'));
    var s3 = new AWS.S3();
    var req = s3.getObject('getObject', {});
    var stream = req.createReadStream();
    stream.pipe(concatStream(function(actual) {
      st.equals(actual.toString(), 'body')
      awsMock.restore('S3', 'getObject');
      st.end();
    }));

[MrHen]

@nelsonic Not sure what help is needed for this ticket. The PR is ready to go. Is there someone else I can ping who can look at this and merge it?

[MrHen]

@nikhilaravi
@jruts
@jcready
@motiz88
@nelsonic

Sorry to ping all of you but I'm not sure which of you is the right person to ask for a merge. If no one has time or interest, feel free to add me as a contributor.

[nelsonic]

@MrHen merged and added you as a colaborator. (not so that you can merge your own PRs, just so that you can review anyone else's in the future and can create branches directly in the project) 👍