Supress Xcode undeclared selector warning

Supressed Xcode undeclared selector warning in SVModalWebViewController.m on line `UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone
                                                                                    target:self.webViewController
                                                                                    action:@selector(doneButtonClicked:)];`

Fix podspec.

Update podspec to 0.2.

Migrate to ARC.