Podspec tweaks/warning fix

Some minor podspec tweaks:

- Use dumb quotes
- Fix up emails
- Add spec tag

Cocoapods will not accept specs that lint with warnings. OvershareKit has one minor warning:

`OvershareKit/Overshare Kit/OSKFacebookUtility.m:48:23: warning: unused variable 'response' [-Wunused-variable]`

Fixed by applying `__unused`.