Added dropbox's API key
Added an Android test project to check the correctness of our code, which is now available in the app folder
Update README.md
Added epublib, a library to manage .epub files
Removed files that were moved to app/
README updated
Initial code version. The dummy LoginActivity launches the Dropbox's login process and then shows the LibraryActivity. LibraryActivity makes use of two fragments to work.

All dropbox interaction is done through the DropboxManager, a singleton class which manages login, logout, listing files and open files. However DropboxManager blocks the UI thread so we must move the blocking code to an AsyncTask.