Basic support for topics

[abiskop]

fixes #7

[evanshortiss]

This looks great @abiskop. I've been busy with work the last few days but should get around to merging this tonight.

[evanshortiss]

@abiskop could you possibly update the README with information on the newly added features?

[abiskop]

Sure! Will do that tomorrow!

EDIT: Did not get to it so far due to stuff@work, but hopefully during the next days.

[evanshortiss]

Thanks for the update @abiskop. I can relate :)

[abiskop]

Alright, README update done!

[evanshortiss]

This is an awesome PR thanks @abiskop! I'll get it published to npm within 24 hours.

👏

[evanshortiss]

@abiskop published to npm registry as version 1.2.0

[abiskop]

Great, thanks! I might also add the remaining topic-/subscription-related methods like "getTopicAttributes" and stuff at some point; I just didn't really need it at this point, that's why I skipped it during the first iteration.
Also, I realized that in many cases, one does not actually need to know the platform(Application(Arn)), e.g. for creating topics, subscribing users etc.; however, it is strictly required that it is passed into the constructor when creating an instance of the interface. We might consider changing the API here at some point so that the platform has to be passed only into methods that actually need it...

[evanshortiss]

Add things only when we need them. The evolutionary development process ;)

[race]

👍