Fixes issue #9: Prevent an IndexOutOfBoundsException by ensuring the tabs have been added to the ActionBar before ActionBar#setSelectedNavigationItem(int) is called.
Prevent JSONException from being thrown (and caught) when unexpected JSON is encountered:
{"alive":"1","last_share_timestamp":null,"hashrate":"int","username":"String"}
{"alive":"1","hashrate":"int","username":"String"}
Merge pull request #10 from justinmuller/issue-9

Fixes issue #9 .
Merge pull request #11 from justinmuller/prevent-JSONException

Prevent `JSONException`