Added support for timeout property in JCNotificationBanner.

JCNotificationBanner supports the property
JCNotificationBannerPresenterIOSStyle and JCNotificationBannerPresenterSmokeStyle respect the property
New method on JCNotificationCenter to support arbitrary custom JCNotificationBanners.
Style fixes. Documented changes in README
Merge pull request #17 from twocanoes/timeout

Banner Timeout Implemented