Allow option to install to SD Card

Edit AndroidManifest.xml to add android:installLocation="auto". This allows the user to choose to install part of the app to their SD Card to help save install space. See also http://code.tutsplus.com/tutorials/quick-tip-enabling-the-android-move-to-sd-card-feature--mobile-862
Merge pull request #12 from JKtheSlacker/master

Allow option to install to SD Card