ConvertApp:

This is a simple currency converter app. 
Its uses data from free, public api to download rates to calculate desired rate in selected currency.
Default currency is `GBP` with amount of 100.0.

Contains:
- soure code for the app in `PaymentApp` folder
- unit tests in `PaymentAppTests` folder

Usage:

- main view presents downloaded rates in collectionView with `GBP` as default currency
- each cell show a flag, short annd long currency name and input
- input can be used to provide given amount of money
- each time user begins to edit that amount, its cell moves to the top
- currencies are refresh on a timer, every 2 seconds with initial 2 seconds delay