isDirectoryExists() always returns true

[Paul Anton]

The result of calling the isDirectoryExists() method on an instance of the internal storage is always true.

Easily checked by writing an androidTest:

@Before
public void setup() {
    Context context = InstrumentationRegistry.getTargetContext();
    storage = SimpleStorage.getInternalStorage(context);
}

@Test
public void shouldCreateTypedFolder() {
    storage.deleteDirectory("sub-" + Type.ONE);
    storage.deleteDirectory("sub-" + Type.ALL);

    // below fails
    assertFalse(storage.isDirectoryExists("sub-" + Type.ALL));

[Roman Kushnarenko]

Fixed in latest version. Same issue #10.