docs: Update the README.md file

Formatting was updated with Markdown. Additional information on contribution and setup was added.

Author: Mehrdad

BitCoin API.xcodeproj/project.xcworkspace/xcuserdata/Mehrdad.xcuserdatad/UserInterfaceState.xcuserstate

@@ -1,20 +1,38 @@
-# Bitcoin-API
+# Bitcoin API
 
 ## Overview
 
-A sample Bitcoin API app that shows the current value of this cryptocurrency in a list of different currencies. This app uses "Bitcoin Average API" to fetch data and was completed as an assignment for Seneca College course in iOS Mobile Application Development. 
+A sample Bitcoin API app that shows the current value of this cryptocurrency in a list of different currencies. This app uses [Bitcoin Average API](https://apiv2.bitcoinaverage.com/) to fetch data and was completed as an assignment for Seneca College course in iOS Mobile Application Development by using fundamental principles as follows:
 
-• GCD and multi-threading
-• UIPickerView
-• GET Request, API & Web Services
-• Parsing JSON
-• Error Handling
+* GCD and multi-threading
+* UIPickerView
+* GET Request, API & Web Services
+* Parsing JSON
+* Error Handling
 
-Language: Swift
+Language: Swift  
 Assignment for: Seneca College - iOS Mobile Application Development course
-The API address: https://apiv2.bitcoinaverage.com/
+
+
+## Resources
+Bitcoin Average API: <https://apiv2.bitcoinaverage.com/>
+
 
 ## Setup
+You need to replace you unique API Key for Bitcoin Average API in the following static property of the `BitcoinAPI` class. This projects needs no additional setup.
+
+```swift
+static let apiKey = "ENTER API KEY HERE"
+```
+
+## Contributing
+
+Feel free to contribute to **Bitcoin API**. Fork and clone this repository, then make a pull request once you have pushed your changes.
+
 
 ## Maintainers
 m-ahmadian
+
+
+## License
+**Bitcoin API** is available under the [MIT License](https://github.com/m-ahmadian/Bitcoin-API/blob/master/LICENSE).