Two fixes to prevent memory leak from occuring.

I'm using Apptentive in one of my apps inside multiple activities, and I was debugging some memory issues. I noticed that some of these activities were being held onto after they've been finished by Apptentive. These two changes seem to fix the issue.

I've also attached a screenshot from Eclipse MemoryAnalyzer showing the problem. The IntroActivity_ that is shown has already been finished. But it still shows up in the memory dump, and when I check the path to GC root these two references show up (along with another library with the same problem).

Let me know if you have any questions.

![eclipse_memory_analyzer](https://f.cloud.github.com/assets/1022833/1443536/cda82316-41e8-11e3-9a1f-1a7d904c530e.png)