Add Gradle dependencies to compile Groovy
FileGetter uses Drive API synchronously, relying on RxJava instead.
Refactoring for simplicity
Added BaseRuntimeException that accepts formatted strings in constructors
FileGetter takes advantage of new BaseRuntimeException
CouldNotGetFileException definition + implementation out of the FileGetter interface
CardListWriter uses Drive API synchronously, relying on RxJava instead
CardListReader uses Drive API synchronously, relying on RxJava instead
Moved exceptions to subpackage
Moved CardNotFoundException to exceptions package
DAO callbacks are executed on the main thread
CardDAO uses the new Observables returned by the Writer
Revert "Add Gradle dependencies to compile Groovy"

This reverts commit d842d2ef639c40e257509c713ac768289a1fa730.
Merge pull request #1 from rulych/asynchronous-management-to-rxjava

Let RxJava manage the asynchronous stuff