Fixed a SQLiteException when calling setItem with a string as the key.

I ran into a SQLiteException when calling setItem() with a string as the key, such as "settings".

The issue is that SQLite thinks "settings" in "_id = settings" as a column name, and reports that the column "settings" can't be found. Adding single quotes around the key fixed the issue. 

http://stackoverflow.com/questions/6337296/sqlite-exception-no-such-column-when-trying-to-select