add observable so we can use it in tests
add observable so we can use it in tests

chrahunt/Dexie.js,jimmywarting/Dexie.js,chrahunt/Dexie.js,dfahlander/Dexie.js,dfahlander/Dexie.js,dfahlander/Dexie.js,dfahlander/Dexie.js,chrahunt/Dexie.js,jimmywarting/Dexie.js,chrahunt/Dexie.js,jimmywarting/Dexie.js,jimmywarting/Dexie.js