### Motivation
Otherwise the `elevation` prop will be passed on to `Animated.View` in `Surface` component and cause this warning on web: You are setting the style `{ elevation: ... }` as a prop. You should nest it in a style object. E.g. `{ style: { elevation: ... } }`
### Test plan
n/a
### Motivation
This PR makes clear what is the cause of app crash when user doesn't wrap his components' tree with Provider component.
### Test plan
Render Portal component without wrapping components' tree with Provider component.
Nice error message with link to our docs will be presented.
### Motivation
Fixes#556. It appears like the default card actions padding is slightly wrong. The issue affects buttons as well.
This is somehow a possibly minor, but breaking change for existing projects, so I'll try to explain what's going on.
### Resources
Cards
According to MD guidelines the card actions padding is 8. The content's padding is 16. Cards use the "compact" buttons with smaller padding - 8 instead of standard 16.
Buttons
The standard horizontal padding is 16. Although it's different for card action buttons. Notice the min-width value, which is 64, but the buttons section doesn't really describe the compact buttons.
### Solution
The example provided by @brunohkbx presented a case where it got caught into the min-width trap. The text was too small and caused a larger button padding. If you run this [expo snack](https://snack.expo.io/HyqcT35KX), it presents the same case, just with different button text. First goes too far to the right, second goes too far to the left.
The first thing to fix was the card actions padding - switch from 4 to 8. It results in:
<img width="377" alt="screen shot 2018-09-27 at 22 21 01" src="https://user-images.githubusercontent.com/7827311/46172934-2a4ecd80-c2a5-11e8-9364-17911a79cce3.png">
So it works for the expo examples case, but not really for the [mentioned issue](#556). It still gives an extra button padding due to too short text (min-width).
After removing the min-width from compact buttons, it seems like it's finally there:
<img width="376" alt="screen shot 2018-09-27 at 22 13 03" src="https://user-images.githubusercontent.com/7827311/46173141-b95be580-c2a5-11e8-88dd-82a15f5981a5.png">
Finally, it also switches the dialog actions to 8 padding, since that's basically the same thing.
### Test plan
https://snack.expo.io/HydBnn5t7
Snapshot tests updated
* feat: initial implementation of banner component.
* feat: add props description.
* refactor: Change the way banner is structured.
* refactor: small refactor of banner component and example.
* refactor: remove some not needed logic from banner and add example.
* refactor: refactor of banner props description and little clean up in component.
* refactor: simplify implementation of banner
* feat: add snapshot tests for banner.
* feat: add banner gif.
* fix: fix example.
* fix: reduce banner gif size.
* fix: reduce gif size even more.
