Also added documentation for EthereumPrivateKey and EthereumAddress and
more tests.

(I got a statgasm again)...

Add parsing abi object fix to README

Enhance signing

Bump BigInt version

We will no longer support Cocoapods and Carthage. They are outdated and
hardly anyone cares about them let alone maintain them.
All Cocoapods and Carthage Users: You can add this package as a Swift
Package in XCode without having to switch away from Cocoapods or
Carthage. They both support optionally adding SPM Packages.

If you don't use XCode 11 or higher you should really switch. XCode 10
and lower is becoming really outdated.

As a matter of fact you should really switch with all SPM ready packages
to SPM. Because it is maintained by Apple and is the official package
manager it is already awesome. And it's not longer in beta. It is used
in productiona nd makes much less problems than Cocoapods. Try switching
with as much as you can and try to slowly replace Cocoapods alltogether.

Updates example URL links (#1)