refactor: migrate notifications screen to styled-components

[ZahraTee]

Screenshots

Before	After

Part of #532.

[coveralls]

Coverage remained the same at 40.544% when pulling 2dad11e on ZahraTee:styled-components-notifications-screen into 5691f00 on gitpoint:master.

[machour]

A little question here too :)

[machour]

Shouldn't TextContainer styled definition read and apply the height prop?

[ZahraTee]

I thought that too but I found that you actually don't need to... It seems that styled.Views can apply values (including height) passed in as props directly and handles null values better. I built out a small example here: https://snack.expo.io/Bys9FZumz

I can change it if it's more explicit but I thought leaving it like this is a bit neater.

[chinesedfan]

styled-components pass on all their props.

From documents, I learned something new. :)

[housseindjirdeh]

This looks perfect, thank you @ZahraTee 🎉