Increase display time of toasts
"Toasts" are the little pop-up messages that display at the bottom of the app, and then disappear automatically. These sometimes flash error messages, as well as success messages such as when the user logs in.
We are using the implementation of toasts that are included in native-base.
However, under the default settings they disappear much too quickly to be read sometimes. We should probably try to find a better display time for them, and maybe a longer fade-out animation.
Unfortunately (last I checked) native-base didn't have an easy way to configure this globally throughout the application. This is easily fixed by just writing our own wrapper around Toast.show to call it with our preferred defaults.