Switch to SharedPreferences.Editor.apply() - Closes #76

From the Android documentation:
"Unlike commit(), which writes its preferences out to persistent
storage synchronously, apply() commits its changes to the in-memory
SharedPreferences immediately but starts an asynchronous commit to
disk. As SharedPreferences instances are singletons within a
process, it's safe to replace any instance of commit() with apply()
if you were already ignoring the return value."

Unfortunately, apply() requires API 9 or higher. Since API 9 devices
don't really exist, and with upcoming features requiring API 10,
the min SDK version is upped to 10.

Signed-off-by: Greg Meiste <greg.meiste@gmail.com>