Errors are not caught in many places

[schmod]

Throughout the library, there are several instances of req.onsuccess = req.onerror, which results in promises resolving when they should have been rejected.

Additionally, many methods within the IndexedDB API can potentially raise DOMExceptions, which are not caught at all by angular-indexedDB. These exceptions can be particularly problematic, because they are often raised within then() blocks inside the library (which makes them impossible to catch from the outside).